[PATCH v2 0/1] nvmem: Handle actual amount of data read/written by suppliers

[PATCH v2 0/1] nvmem: Handle actual amount of data read/written by suppliers

[Joy Chakraborty]

This Patch series stems from discussions in patchset,
"[PATCH v2] nvmem: rmem: Fix return value of rmem_read()"
(https://lore.kernel.org/all/20240206042408.224138-1-joychakr@google.com/).
Where we come across the fact that currently the nvmem suppliers do not
actually let the core know how much data has been actually read or written.
Instead they are expected to return 0 for success and the core assumes that
the amount of data written is equal to what the core has requested.

On addition this patchset will also add some guards and checks based on the
count of data returned by the nvmem supplier.
---
V2 Changes : Rebase on for-next.
---
V1 Changes : Change read/write callback prototype to ssize_t and
supplier changes to accomodate the same with core checks and bounds.
---

Joy Chakraborty (1):
  nvmem: Change return type of reg read/write to ssize_t

 drivers/nvmem/apple-efuses.c        |  7 +--
 drivers/nvmem/bcm-ocotp.c           | 12 ++---
 drivers/nvmem/brcm_nvram.c          | 10 ++--
 drivers/nvmem/core.c                | 83 +++++++++++++----------------
 drivers/nvmem/imx-iim.c             |  6 +--
 drivers/nvmem/imx-ocotp-ele.c       |  4 +-
 drivers/nvmem/imx-ocotp-scu.c       | 12 ++---
 drivers/nvmem/imx-ocotp.c           | 10 ++--
 drivers/nvmem/jz4780-efuse.c        |  7 +--
 drivers/nvmem/lan9662-otpc.c        | 12 ++---
 drivers/nvmem/layerscape-sfp.c      | 11 ++--
 drivers/nvmem/lpc18xx_eeprom.c      | 14 ++---
 drivers/nvmem/lpc18xx_otp.c         |  6 +--
 drivers/nvmem/meson-efuse.c         | 22 +++++---
 drivers/nvmem/meson-mx-efuse.c      |  6 +--
 drivers/nvmem/microchip-otpc.c      |  6 +--
 drivers/nvmem/mtk-efuse.c           |  6 +--
 drivers/nvmem/mxs-ocotp.c           |  7 +--
 drivers/nvmem/nintendo-otp.c        |  6 +--
 drivers/nvmem/qcom-spmi-sdam.c      | 12 ++---
 drivers/nvmem/qfprom.c              | 14 ++---
 drivers/nvmem/qoriq-efuse.c         |  6 +--
 drivers/nvmem/rave-sp-eeprom.c      | 18 +++----
 drivers/nvmem/rmem.c                |  4 +-
 drivers/nvmem/rockchip-efuse.c      | 19 +++----
 drivers/nvmem/rockchip-otp.c        | 19 +++----
 drivers/nvmem/sc27xx-efuse.c        |  3 +-
 drivers/nvmem/sec-qfprom.c          |  4 +-
 drivers/nvmem/snvs_lpgpr.c          | 17 +++---
 drivers/nvmem/sprd-efuse.c          |  8 +--
 drivers/nvmem/stm32-bsec-optee-ta.c | 12 ++---
 drivers/nvmem/stm32-bsec-optee-ta.h | 20 +++----
 drivers/nvmem/stm32-romem.c         | 26 ++++-----
 drivers/nvmem/sunplus-ocotp.c       |  4 +-
 drivers/nvmem/sunxi_sid.c           | 15 +++---
 drivers/nvmem/u-boot-env.c          |  6 +--
 drivers/nvmem/uniphier-efuse.c      |  6 +--
 drivers/nvmem/vf610-ocotp.c         |  7 +--
 drivers/nvmem/zynqmp_nvmem.c        | 13 ++---
 include/linux/nvmem-provider.h      |  4 +-
 40 files changed, 253 insertions(+), 231 deletions(-)

-- 
2.44.0.769.g3c40516874-goog

[PATCH v2 1/1] nvmem: Change return type of reg read/write to ssize_t

[Joy Chakraborty]

Change return type of reg_read() and reg_write() callback to ssize_t for
nvmem suppliers to return number of bytes read/written to the nvmem core.

Currently nvmem core assumes the amount of data read/written is equal
to what it has requested from the supplier, this return code facilitates
better error handling in the nvmem core.

Signed-off-by: Joy Chakraborty <joychakr@google.com>
---
 drivers/nvmem/apple-efuses.c        |  7 +--
 drivers/nvmem/bcm-ocotp.c           | 12 ++---
 drivers/nvmem/brcm_nvram.c          | 10 ++--
 drivers/nvmem/core.c                | 83 +++++++++++++----------------
 drivers/nvmem/imx-iim.c             |  6 +--
 drivers/nvmem/imx-ocotp-ele.c       |  4 +-
 drivers/nvmem/imx-ocotp-scu.c       | 12 ++---
 drivers/nvmem/imx-ocotp.c           | 10 ++--
 drivers/nvmem/jz4780-efuse.c        |  7 +--
 drivers/nvmem/lan9662-otpc.c        | 12 ++---
 drivers/nvmem/layerscape-sfp.c      | 11 ++--
 drivers/nvmem/lpc18xx_eeprom.c      | 14 ++---
 drivers/nvmem/lpc18xx_otp.c         |  6 +--
 drivers/nvmem/meson-efuse.c         | 22 +++++---
 drivers/nvmem/meson-mx-efuse.c      |  6 +--
 drivers/nvmem/microchip-otpc.c      |  6 +--
 drivers/nvmem/mtk-efuse.c           |  6 +--
 drivers/nvmem/mxs-ocotp.c           |  7 +--
 drivers/nvmem/nintendo-otp.c        |  6 +--
 drivers/nvmem/qcom-spmi-sdam.c      | 12 ++---
 drivers/nvmem/qfprom.c              | 14 ++---
 drivers/nvmem/qoriq-efuse.c         |  6 +--
 drivers/nvmem/rave-sp-eeprom.c      | 18 +++----
 drivers/nvmem/rmem.c                |  4 +-
 drivers/nvmem/rockchip-efuse.c      | 19 +++----
 drivers/nvmem/rockchip-otp.c        | 19 +++----
 drivers/nvmem/sc27xx-efuse.c        |  3 +-
 drivers/nvmem/sec-qfprom.c          |  4 +-
 drivers/nvmem/snvs_lpgpr.c          | 17 +++---
 drivers/nvmem/sprd-efuse.c          |  8 +--
 drivers/nvmem/stm32-bsec-optee-ta.c | 12 ++---
 drivers/nvmem/stm32-bsec-optee-ta.h | 20 +++----
 drivers/nvmem/stm32-romem.c         | 26 ++++-----
 drivers/nvmem/sunplus-ocotp.c       |  4 +-
 drivers/nvmem/sunxi_sid.c           | 15 +++---
 drivers/nvmem/u-boot-env.c          |  6 +--
 drivers/nvmem/uniphier-efuse.c      |  6 +--
 drivers/nvmem/vf610-ocotp.c         |  7 +--
 drivers/nvmem/zynqmp_nvmem.c        | 13 ++---
 include/linux/nvmem-provider.h      |  4 +-
 40 files changed, 253 insertions(+), 231 deletions(-)

diff --git a/drivers/nvmem/apple-efuses.c b/drivers/nvmem/apple-efuses.c
index d3d49d22338b..c97328ee220a 100644
--- a/drivers/nvmem/apple-efuses.c
+++ b/drivers/nvmem/apple-efuses.c
@@ -15,10 +15,11 @@ struct apple_efuses_priv {
 	void __iomem *fuses;
 };
 
-static int apple_efuses_read(void *context, unsigned int offset, void *val,
-			     size_t bytes)
+static ssize_t apple_efuses_read(void *context, unsigned int offset, void *val,
+				 size_t bytes)
 {
 	struct apple_efuses_priv *priv = context;
+	size_t bytes_read = bytes;
 	u32 *dst = val;
 
 	while (bytes >= sizeof(u32)) {
@@ -27,7 +28,7 @@ static int apple_efuses_read(void *context, unsigned int offset, void *val,
 		offset += sizeof(u32);
 	}
 
-	return 0;
+	return bytes_read;
 }
 
 static int apple_efuses_probe(struct platform_device *pdev)
diff --git a/drivers/nvmem/bcm-ocotp.c b/drivers/nvmem/bcm-ocotp.c
index 2490f44caa40..9435002787bd 100644
--- a/drivers/nvmem/bcm-ocotp.c
+++ b/drivers/nvmem/bcm-ocotp.c
@@ -148,8 +148,8 @@ static int disable_ocotp_program(void __iomem *base)
 	return ret;
 }
 
-static int bcm_otpc_read(void *context, unsigned int offset, void *val,
-	size_t bytes)
+static ssize_t bcm_otpc_read(void *context, unsigned int offset, void *val,
+			     size_t bytes)
 {
 	struct otpc_priv *priv = context;
 	u32 *buf = val;
@@ -176,11 +176,11 @@ static int bcm_otpc_read(void *context, unsigned int offset, void *val,
 		reset_start_bit(priv->base);
 	}
 
-	return 0;
+	return bytes_read;
 }
 
-static int bcm_otpc_write(void *context, unsigned int offset, void *val,
-	size_t bytes)
+static ssize_t bcm_otpc_write(void *context, unsigned int offset, void *val,
+			      size_t bytes)
 {
 	struct otpc_priv *priv = context;
 	u32 *buf = val;
@@ -214,7 +214,7 @@ static int bcm_otpc_write(void *context, unsigned int offset, void *val,
 
 	disable_ocotp_program(priv->base);
 
-	return 0;
+	return bytes_written;
 }
 
 static struct nvmem_config bcm_otpc_nvmem_config = {
diff --git a/drivers/nvmem/brcm_nvram.c b/drivers/nvmem/brcm_nvram.c
index 5cdf339cfbec..dd0e52eb12bd 100644
--- a/drivers/nvmem/brcm_nvram.c
+++ b/drivers/nvmem/brcm_nvram.c
@@ -46,8 +46,8 @@ struct brcm_nvram_header {
 	__le32 config_ncdl;	/* ncdl values for memc */
 };
 
-static int brcm_nvram_read(void *context, unsigned int offset, void *val,
-			   size_t bytes)
+static ssize_t brcm_nvram_read(void *context, unsigned int offset, void *val,
+			       size_t bytes)
 {
 	struct brcm_nvram *priv = context;
 	size_t to_copy;
@@ -61,7 +61,11 @@ static int brcm_nvram_read(void *context, unsigned int offset, void *val,
 
 	memset((uint8_t *)val + to_copy, priv->padding_byte, bytes - to_copy);
 
-	return 0;
+	/*
+	 * Returning bytes requested as the whole buffer is padded even if the
+	 * requested bytes to be read is out of bounds of resource size.
+	 */
+	return bytes;
 }
 
 static int brcm_nvram_copy_data(struct brcm_nvram *priv, struct platform_device *pdev)
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index e1ec3b7200d7..a41b29e60e58 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -55,8 +55,8 @@ static LIST_HEAD(nvmem_lookup_list);
 
 static BLOCKING_NOTIFIER_HEAD(nvmem_notifier);
 
-static int __nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset,
-			    void *val, size_t bytes)
+static ssize_t __nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset,
+				void *val, size_t bytes)
 {
 	if (nvmem->reg_read)
 		return nvmem->reg_read(nvmem->priv, offset, val, bytes);
@@ -64,10 +64,10 @@ static int __nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset,
 	return -EINVAL;
 }
 
-static int __nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset,
-			     void *val, size_t bytes)
+static ssize_t __nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset,
+				 void *val, size_t bytes)
 {
-	int ret;
+	ssize_t ret;
 
 	if (nvmem->reg_write) {
 		gpiod_set_value_cansleep(nvmem->wp_gpio, 0);
@@ -79,8 +79,8 @@ static int __nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset,
 	return -EINVAL;
 }
 
-static int nvmem_access_with_keepouts(struct nvmem_device *nvmem,
-				      unsigned int offset, void *val,
+static ssize_t nvmem_access_with_keepouts(struct nvmem_device *nvmem,
+					  unsigned int offset, void *val,
 				      size_t bytes, int write)
 {
 
@@ -88,7 +88,7 @@ static int nvmem_access_with_keepouts(struct nvmem_device *nvmem,
 	unsigned int kend, ksize;
 	const struct nvmem_keepout *keepout = nvmem->keepout;
 	const struct nvmem_keepout *keepoutend = keepout + nvmem->nkeepout;
-	int rc;
+	ssize_t rc, count = 0;
 
 	/*
 	 * Skip all keepouts before the range being accessed.
@@ -107,11 +107,12 @@ static int nvmem_access_with_keepouts(struct nvmem_device *nvmem,
 			else
 				rc = __nvmem_reg_read(nvmem, offset, val, ksize);
 
-			if (rc)
+			if (rc < 0)
 				return rc;
 
 			offset += ksize;
 			val += ksize;
+			count += rc;
 		}
 
 		/*
@@ -135,16 +136,21 @@ static int nvmem_access_with_keepouts(struct nvmem_device *nvmem,
 	if (offset < end) {
 		ksize = end - offset;
 		if (write)
-			return __nvmem_reg_write(nvmem, offset, val, ksize);
+			rc = __nvmem_reg_write(nvmem, offset, val, ksize);
 		else
-			return __nvmem_reg_read(nvmem, offset, val, ksize);
+			rc = __nvmem_reg_read(nvmem, offset, val, ksize);
+
+		if (rc < 0)
+			return rc;
+
+		count += rc;
 	}
 
-	return 0;
+	return count;
 }
 
-static int nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset,
-			  void *val, size_t bytes)
+static ssize_t nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset,
+			      void *val, size_t bytes)
 {
 	if (!nvmem->nkeepout)
 		return __nvmem_reg_read(nvmem, offset, val, bytes);
@@ -152,8 +158,8 @@ static int nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset,
 	return nvmem_access_with_keepouts(nvmem, offset, val, bytes, false);
 }
 
-static int nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset,
-			   void *val, size_t bytes)
+static ssize_t nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset,
+			       void *val, size_t bytes)
 {
 	if (!nvmem->nkeepout)
 		return __nvmem_reg_write(nvmem, offset, val, bytes);
@@ -195,7 +201,6 @@ static ssize_t bin_attr_nvmem_read(struct file *filp, struct kobject *kobj,
 {
 	struct device *dev;
 	struct nvmem_device *nvmem;
-	int rc;
 
 	if (attr->private)
 		dev = attr->private;
@@ -221,12 +226,7 @@ static ssize_t bin_attr_nvmem_read(struct file *filp, struct kobject *kobj,
 	if (!nvmem->reg_read)
 		return -EPERM;
 
-	rc = nvmem_reg_read(nvmem, pos, buf, count);
-
-	if (rc)
-		return rc;
-
-	return count;
+	return nvmem_reg_read(nvmem, pos, buf, count);
 }
 
 static ssize_t bin_attr_nvmem_write(struct file *filp, struct kobject *kobj,
@@ -235,7 +235,6 @@ static ssize_t bin_attr_nvmem_write(struct file *filp, struct kobject *kobj,
 {
 	struct device *dev;
 	struct nvmem_device *nvmem;
-	int rc;
 
 	if (attr->private)
 		dev = attr->private;
@@ -261,12 +260,7 @@ static ssize_t bin_attr_nvmem_write(struct file *filp, struct kobject *kobj,
 	if (!nvmem->reg_write)
 		return -EPERM;
 
-	rc = nvmem_reg_write(nvmem, pos, buf, count);
-
-	if (rc)
-		return rc;
-
-	return count;
+	return nvmem_reg_write(nvmem, pos, buf, count);
 }
 
 static umode_t nvmem_bin_attr_get_umode(struct nvmem_device *nvmem)
@@ -1638,9 +1632,12 @@ static int __nvmem_cell_read(struct nvmem_device *nvmem,
 
 	rc = nvmem_reg_read(nvmem, cell->offset, buf, cell->raw_len);
 
-	if (rc)
+	if (rc < 0)
 		return rc;
 
+	if (rc != cell->raw_len)
+		return -EIO;
+
 	/* shift bits in-place */
 	if (cell->bit_offset || cell->nbits)
 		nvmem_shift_read_buffer_in_place(cell, buf);
@@ -1713,8 +1710,11 @@ static void *nvmem_cell_prepare_write_buffer(struct nvmem_cell_entry *cell,
 
 		/* setup the first byte with lsb bits from nvmem */
 		rc = nvmem_reg_read(nvmem, cell->offset, &v, 1);
-		if (rc)
+		if (rc < 1) {
+			if (rc == 0)
+				rc = -EIO;
 			goto err;
+		}
 		*b++ |= GENMASK(bit_offset - 1, 0) & v;
 
 		/* setup rest of the byte if any */
@@ -1733,8 +1733,11 @@ static void *nvmem_cell_prepare_write_buffer(struct nvmem_cell_entry *cell,
 		/* setup the last byte with msb bits from nvmem */
 		rc = nvmem_reg_read(nvmem,
 				    cell->offset + cell->bytes - 1, &v, 1);
-		if (rc)
+		if (rc < 1) {
+			if (rc == 0)
+				rc = -EIO;
 			goto err;
+		}
 		*p |= GENMASK(7, (nbits + bit_offset) % BITS_PER_BYTE) & v;
 
 	}
@@ -1774,10 +1777,7 @@ static int __nvmem_cell_entry_write(struct nvmem_cell_entry *cell, void *buf, si
 	if (cell->bit_offset || cell->nbits)
 		kfree(buf);
 
-	if (rc)
-		return rc;
-
-	return len;
+	return rc;
 }
 
 /**
@@ -2052,17 +2052,10 @@ int nvmem_device_read(struct nvmem_device *nvmem,
 		      unsigned int offset,
 		      size_t bytes, void *buf)
 {
-	int rc;
-
 	if (!nvmem)
 		return -EINVAL;
 
-	rc = nvmem_reg_read(nvmem, offset, buf, bytes);
-
-	if (rc)
-		return rc;
-
-	return bytes;
+	return nvmem_reg_read(nvmem, offset, buf, bytes);
 }
 EXPORT_SYMBOL_GPL(nvmem_device_read);
 
diff --git a/drivers/nvmem/imx-iim.c b/drivers/nvmem/imx-iim.c
index f13bbd164086..f9f912bd4e41 100644
--- a/drivers/nvmem/imx-iim.c
+++ b/drivers/nvmem/imx-iim.c
@@ -29,8 +29,8 @@ struct iim_priv {
 	struct clk *clk;
 };
 
-static int imx_iim_read(void *context, unsigned int offset,
-			  void *buf, size_t bytes)
+static ssize_t imx_iim_read(void *context, unsigned int offset,
+			    void *buf, size_t bytes)
 {
 	struct iim_priv *iim = context;
 	int i, ret;
@@ -49,7 +49,7 @@ static int imx_iim_read(void *context, unsigned int offset,
 
 	clk_disable_unprepare(iim->clk);
 
-	return 0;
+	return bytes;
 }
 
 static struct imx_iim_drvdata imx27_drvdata = {
diff --git a/drivers/nvmem/imx-ocotp-ele.c b/drivers/nvmem/imx-ocotp-ele.c
index cf920542f939..3025fe8aa991 100644
--- a/drivers/nvmem/imx-ocotp-ele.c
+++ b/drivers/nvmem/imx-ocotp-ele.c
@@ -61,7 +61,7 @@ static enum fuse_type imx_ocotp_fuse_type(void *context, u32 index)
 	return FUSE_INVALID;
 }
 
-static int imx_ocotp_reg_read(void *context, unsigned int offset, void *val, size_t bytes)
+static ssize_t imx_ocotp_reg_read(void *context, unsigned int offset, void *val, size_t bytes)
 {
 	struct imx_ocotp_priv *priv = context;
 	void __iomem *reg = priv->base + priv->data->reg_off;
@@ -102,7 +102,7 @@ static int imx_ocotp_reg_read(void *context, unsigned int offset, void *val, siz
 
 	kfree(p);
 
-	return 0;
+	return bytes;
 };
 
 static int imx_ele_ocotp_probe(struct platform_device *pdev)
diff --git a/drivers/nvmem/imx-ocotp-scu.c b/drivers/nvmem/imx-ocotp-scu.c
index 517d83e11af2..033261827141 100644
--- a/drivers/nvmem/imx-ocotp-scu.c
+++ b/drivers/nvmem/imx-ocotp-scu.c
@@ -129,8 +129,8 @@ static int imx_sc_misc_otp_fuse_read(struct imx_sc_ipc *ipc, u32 word,
 	return 0;
 }
 
-static int imx_scu_ocotp_read(void *context, unsigned int offset,
-			      void *val, size_t bytes)
+static ssize_t imx_scu_ocotp_read(void *context, unsigned int offset,
+				  void *val, size_t bytes)
 {
 	struct ocotp_priv *priv = context;
 	u32 count, index, num_bytes;
@@ -174,11 +174,11 @@ static int imx_scu_ocotp_read(void *context, unsigned int offset,
 
 	kfree(p);
 
-	return 0;
+	return bytes;
 }
 
-static int imx_scu_ocotp_write(void *context, unsigned int offset,
-			       void *val, size_t bytes)
+static ssize_t imx_scu_ocotp_write(void *context, unsigned int offset,
+				   void *val, size_t bytes)
 {
 	struct ocotp_priv *priv = context;
 	struct arm_smccc_res res;
@@ -215,7 +215,7 @@ static int imx_scu_ocotp_write(void *context, unsigned int offset,
 
 	mutex_unlock(&scu_ocotp_mutex);
 
-	return res.a0;
+	return res.a0 < 0 ? res.a0 : bytes;
 }
 
 static struct nvmem_config imx_scu_ocotp_nvmem_config = {
diff --git a/drivers/nvmem/imx-ocotp.c b/drivers/nvmem/imx-ocotp.c
index 79dd4fda0329..4338bc83665a 100644
--- a/drivers/nvmem/imx-ocotp.c
+++ b/drivers/nvmem/imx-ocotp.c
@@ -154,8 +154,8 @@ static void imx_ocotp_clr_err_if_set(struct ocotp_priv *priv)
 	writel(bm_ctrl_error, base + IMX_OCOTP_ADDR_CTRL_CLR);
 }
 
-static int imx_ocotp_read(void *context, unsigned int offset,
-			  void *val, size_t bytes)
+static ssize_t imx_ocotp_read(void *context, unsigned int offset,
+			      void *val, size_t bytes)
 {
 	struct ocotp_priv *priv = context;
 	unsigned int count;
@@ -217,7 +217,7 @@ static int imx_ocotp_read(void *context, unsigned int offset,
 
 	kfree(p);
 
-	return ret;
+	return ret < 0 ? ret : bytes;
 }
 
 static int imx_ocotp_cell_pp(void *context, const char *id, int index,
@@ -307,8 +307,8 @@ static void imx_ocotp_set_imx7_timing(struct ocotp_priv *priv)
 	writel(timing, priv->base + IMX_OCOTP_ADDR_TIMING);
 }
 
-static int imx_ocotp_write(void *context, unsigned int offset, void *val,
-			   size_t bytes)
+static ssize_t imx_ocotp_write(void *context, unsigned int offset, void *val,
+			       size_t bytes)
 {
 	struct ocotp_priv *priv = context;
 	u32 *buf = val;
diff --git a/drivers/nvmem/jz4780-efuse.c b/drivers/nvmem/jz4780-efuse.c
index 0b01b840edd9..606a63232c3d 100644
--- a/drivers/nvmem/jz4780-efuse.c
+++ b/drivers/nvmem/jz4780-efuse.c
@@ -66,10 +66,11 @@ struct jz4780_efuse {
 };
 
 /* main entry point */
-static int jz4780_efuse_read(void *context, unsigned int offset,
-			     void *val, size_t bytes)
+static ssize_t jz4780_efuse_read(void *context, unsigned int offset,
+				 void *val, size_t bytes)
 {
 	struct jz4780_efuse *efuse = context;
+	size_t bytes_read = bytes;
 
 	while (bytes > 0) {
 		size_t start = offset & ~(JZ_EFU_READ_SIZE - 1);
@@ -112,7 +113,7 @@ static int jz4780_efuse_read(void *context, unsigned int offset,
 		bytes -= chunk;
 	}
 
-	return 0;
+	return bytes_read;
 }
 
 static struct nvmem_config jz4780_efuse_nvmem_config = {
diff --git a/drivers/nvmem/lan9662-otpc.c b/drivers/nvmem/lan9662-otpc.c
index 56fc19f092a7..4a2aa3324b2d 100644
--- a/drivers/nvmem/lan9662-otpc.c
+++ b/drivers/nvmem/lan9662-otpc.c
@@ -119,8 +119,8 @@ static int lan9662_otp_write_byte(struct lan9662_otp *otp, u32 offset, u8 data)
 	return rc;
 }
 
-static int lan9662_otp_read(void *context, unsigned int offset,
-			    void *_val, size_t bytes)
+static ssize_t lan9662_otp_read(void *context, unsigned int offset,
+				void *_val, size_t bytes)
 {
 	struct lan9662_otp *otp = context;
 	u8 *val = _val;
@@ -136,11 +136,11 @@ static int lan9662_otp_read(void *context, unsigned int offset,
 	}
 	lan9662_otp_power(otp, false);
 
-	return rc;
+	return rc < 0 ? rc : bytes;
 }
 
-static int lan9662_otp_write(void *context, unsigned int offset,
-			     void *_val, size_t bytes)
+static ssize_t lan9662_otp_write(void *context, unsigned int offset,
+				 void *_val, size_t bytes)
 {
 	struct lan9662_otp *otp = context;
 	u8 *val = _val;
@@ -167,7 +167,7 @@ static int lan9662_otp_write(void *context, unsigned int offset,
 	}
 	lan9662_otp_power(otp, false);
 
-	return rc;
+	return rc < 0 ? rc : bytes;
 }
 
 static struct nvmem_config otp_config = {
diff --git a/drivers/nvmem/layerscape-sfp.c b/drivers/nvmem/layerscape-sfp.c
index e2b424561949..fdff3374b5a4 100644
--- a/drivers/nvmem/layerscape-sfp.c
+++ b/drivers/nvmem/layerscape-sfp.c
@@ -26,14 +26,17 @@ struct layerscape_sfp_data {
 	enum regmap_endian endian;
 };
 
-static int layerscape_sfp_read(void *context, unsigned int offset, void *val,
-			       size_t bytes)
+static ssize_t layerscape_sfp_read(void *context, unsigned int offset, void *val,
+				   size_t bytes)
 {
 	struct layerscape_sfp_priv *priv = context;
+	int ret;
 
-	return regmap_bulk_read(priv->regmap,
-				LAYERSCAPE_SFP_OTP_OFFSET + offset, val,
+	ret = regmap_bulk_read(priv->regmap,
+			       LAYERSCAPE_SFP_OTP_OFFSET + offset, val,
 				bytes / 4);
+
+	return ret < 0 ? ret : bytes;
 }
 
 static struct nvmem_config layerscape_sfp_nvmem_config = {
diff --git a/drivers/nvmem/lpc18xx_eeprom.c b/drivers/nvmem/lpc18xx_eeprom.c
index a73acc7377d2..1f68731ff865 100644
--- a/drivers/nvmem/lpc18xx_eeprom.c
+++ b/drivers/nvmem/lpc18xx_eeprom.c
@@ -87,10 +87,11 @@ static int lpc18xx_eeprom_busywait_until_prog(struct lpc18xx_eeprom_dev *eeprom)
 	return -ETIMEDOUT;
 }
 
-static int lpc18xx_eeprom_gather_write(void *context, unsigned int reg,
-				       void *val, size_t bytes)
+static ssize_t lpc18xx_eeprom_gather_write(void *context, unsigned int reg,
+					   void *val, size_t bytes)
 {
 	struct lpc18xx_eeprom_dev *eeprom = context;
+	size_t bytes_written = bytes;
 	unsigned int offset = reg;
 	int ret;
 
@@ -123,13 +124,14 @@ static int lpc18xx_eeprom_gather_write(void *context, unsigned int reg,
 	lpc18xx_eeprom_writel(eeprom, LPC18XX_EEPROM_PWRDWN,
 			      LPC18XX_EEPROM_PWRDWN_YES);
 
-	return 0;
+	return bytes_written;
 }
 
-static int lpc18xx_eeprom_read(void *context, unsigned int offset,
-			       void *val, size_t bytes)
+static ssize_t lpc18xx_eeprom_read(void *context, unsigned int offset,
+				   void *val, size_t bytes)
 {
 	struct lpc18xx_eeprom_dev *eeprom = context;
+	size_t bytes_read = bytes;
 
 	lpc18xx_eeprom_writel(eeprom, LPC18XX_EEPROM_PWRDWN,
 			      LPC18XX_EEPROM_PWRDWN_NO);
@@ -147,7 +149,7 @@ static int lpc18xx_eeprom_read(void *context, unsigned int offset,
 	lpc18xx_eeprom_writel(eeprom, LPC18XX_EEPROM_PWRDWN,
 			      LPC18XX_EEPROM_PWRDWN_YES);
 
-	return 0;
+	return bytes_read;
 }
 
 
diff --git a/drivers/nvmem/lpc18xx_otp.c b/drivers/nvmem/lpc18xx_otp.c
index adc9948e7b2e..c60a565b6b97 100644
--- a/drivers/nvmem/lpc18xx_otp.c
+++ b/drivers/nvmem/lpc18xx_otp.c
@@ -37,8 +37,8 @@ struct lpc18xx_otp {
 	void __iomem *base;
 };
 
-static int lpc18xx_otp_read(void *context, unsigned int offset,
-			    void *val, size_t bytes)
+static ssize_t lpc18xx_otp_read(void *context, unsigned int offset,
+				void *val, size_t bytes)
 {
 	struct lpc18xx_otp *otp = context;
 	unsigned int count = bytes >> 2;
@@ -52,7 +52,7 @@ static int lpc18xx_otp_read(void *context, unsigned int offset,
 	for (i = index; i < (index + count); i++)
 		*buf++ = readl(otp->base + i * LPC18XX_OTP_WORD_SIZE);
 
-	return 0;
+	return bytes;
 }
 
 static struct nvmem_config lpc18xx_otp_nvmem_config = {
diff --git a/drivers/nvmem/meson-efuse.c b/drivers/nvmem/meson-efuse.c
index 33678d0af2c2..ed2124d916fc 100644
--- a/drivers/nvmem/meson-efuse.c
+++ b/drivers/nvmem/meson-efuse.c
@@ -14,22 +14,28 @@
 
 #include <linux/firmware/meson/meson_sm.h>
 
-static int meson_efuse_read(void *context, unsigned int offset,
-			    void *val, size_t bytes)
+static ssize_t meson_efuse_read(void *context, unsigned int offset,
+				void *val, size_t bytes)
 {
 	struct meson_sm_firmware *fw = context;
+	int ret;
 
-	return meson_sm_call_read(fw, (u8 *)val, bytes, SM_EFUSE_READ, offset,
-				  bytes, 0, 0, 0);
+	ret = meson_sm_call_read(fw, (u8 *)val, bytes, SM_EFUSE_READ, offset,
+				 bytes, 0, 0, 0);
+
+	return ret < 0 ? ret : bytes;
 }
 
-static int meson_efuse_write(void *context, unsigned int offset,
-			     void *val, size_t bytes)
+static ssize_t meson_efuse_write(void *context, unsigned int offset,
+				 void *val, size_t bytes)
 {
 	struct meson_sm_firmware *fw = context;
+	int ret;
+
+	ret = meson_sm_call_write(fw, (u8 *)val, bytes, SM_EFUSE_WRITE, offset,
+				  bytes, 0, 0, 0);
 
-	return meson_sm_call_write(fw, (u8 *)val, bytes, SM_EFUSE_WRITE, offset,
-				   bytes, 0, 0, 0);
+	return ret < 0 ? ret : bytes;
 }
 
 static const struct of_device_id meson_efuse_match[] = {
diff --git a/drivers/nvmem/meson-mx-efuse.c b/drivers/nvmem/meson-mx-efuse.c
index 8a16f5f02657..de51841216c1 100644
--- a/drivers/nvmem/meson-mx-efuse.c
+++ b/drivers/nvmem/meson-mx-efuse.c
@@ -131,8 +131,8 @@ static int meson_mx_efuse_read_addr(struct meson_mx_efuse *efuse,
 	return 0;
 }
 
-static int meson_mx_efuse_read(void *context, unsigned int offset,
-			       void *buf, size_t bytes)
+static ssize_t meson_mx_efuse_read(void *context, unsigned int offset,
+				   void *buf, size_t bytes)
 {
 	struct meson_mx_efuse *efuse = context;
 	u32 tmp;
@@ -162,7 +162,7 @@ static int meson_mx_efuse_read(void *context, unsigned int offset,
 
 	meson_mx_efuse_hw_disable(efuse);
 
-	return err;
+	return err < 0 ? err : bytes;
 }
 
 static const struct meson_mx_efuse_platform_data meson6_efuse_data = {
diff --git a/drivers/nvmem/microchip-otpc.c b/drivers/nvmem/microchip-otpc.c
index 7cf81738a3e0..c47fdb169734 100644
--- a/drivers/nvmem/microchip-otpc.c
+++ b/drivers/nvmem/microchip-otpc.c
@@ -143,8 +143,8 @@ static int mchp_otpc_prepare_read(struct mchp_otpc *otpc,
  * packet. The user will have to be aware of the memory footprint before doing
  * the read request.
  */
-static int mchp_otpc_read(void *priv, unsigned int off, void *val,
-			  size_t bytes)
+static ssize_t mchp_otpc_read(void *priv, unsigned int off, void *val,
+			      size_t bytes)
 {
 	struct mchp_otpc *otpc = priv;
 	struct mchp_otpc_packet *packet;
@@ -187,7 +187,7 @@ static int mchp_otpc_read(void *priv, unsigned int off, void *val,
 		} while (payload_size >= 0 && len < bytes);
 	}
 
-	return 0;
+	return len;
 }
 
 static int mchp_otpc_init_packets_list(struct mchp_otpc *otpc, u32 *size)
diff --git a/drivers/nvmem/mtk-efuse.c b/drivers/nvmem/mtk-efuse.c
index 9caf04667341..d9db85933ed6 100644
--- a/drivers/nvmem/mtk-efuse.c
+++ b/drivers/nvmem/mtk-efuse.c
@@ -20,8 +20,8 @@ struct mtk_efuse_priv {
 	void __iomem *base;
 };
 
-static int mtk_reg_read(void *context,
-			unsigned int reg, void *_val, size_t bytes)
+static ssize_t mtk_reg_read(void *context,
+			    unsigned int reg, void *_val, size_t bytes)
 {
 	struct mtk_efuse_priv *priv = context;
 	void __iomem *addr = priv->base + reg;
@@ -31,7 +31,7 @@ static int mtk_reg_read(void *context,
 	for (i = 0; i < bytes; i++, val++)
 		*val = readb(addr + i);
 
-	return 0;
+	return bytes;
 }
 
 static int mtk_efuse_gpu_speedbin_pp(void *context, const char *id, int index,
diff --git a/drivers/nvmem/mxs-ocotp.c b/drivers/nvmem/mxs-ocotp.c
index 7b78f18f9545..50734489fb3a 100644
--- a/drivers/nvmem/mxs-ocotp.c
+++ b/drivers/nvmem/mxs-ocotp.c
@@ -56,10 +56,11 @@ static int mxs_ocotp_wait(struct mxs_ocotp *otp)
 	return 0;
 }
 
-static int mxs_ocotp_read(void *context, unsigned int offset,
-			  void *val, size_t bytes)
+static ssize_t mxs_ocotp_read(void *context, unsigned int offset,
+			      void *val, size_t bytes)
 {
 	struct mxs_ocotp *otp = context;
+	size_t bytes_read = bytes;
 	u32 *buf = val;
 	int ret;
 
@@ -102,7 +103,7 @@ static int mxs_ocotp_read(void *context, unsigned int offset,
 disable_clk:
 	clk_disable(otp->clk);
 
-	return ret;
+	return ret < 0 ? ret : bytes_read;
 }
 
 static struct nvmem_config ocotp_config = {
diff --git a/drivers/nvmem/nintendo-otp.c b/drivers/nvmem/nintendo-otp.c
index 355e7f1fc6d5..bcc5246517ae 100644
--- a/drivers/nvmem/nintendo-otp.c
+++ b/drivers/nvmem/nintendo-otp.c
@@ -45,8 +45,8 @@ static const struct nintendo_otp_devtype_data latte_otp_data = {
 	.num_banks = 8,
 };
 
-static int nintendo_otp_reg_read(void *context,
-				 unsigned int reg, void *_val, size_t bytes)
+static ssize_t nintendo_otp_reg_read(void *context,
+				     unsigned int reg, void *_val, size_t bytes)
 {
 	struct nintendo_otp_priv *priv = context;
 	u32 *val = _val;
@@ -61,7 +61,7 @@ static int nintendo_otp_reg_read(void *context,
 		reg += WORD_SIZE;
 	}
 
-	return 0;
+	return bytes;
 }
 
 static const struct of_device_id nintendo_otp_of_table[] = {
diff --git a/drivers/nvmem/qcom-spmi-sdam.c b/drivers/nvmem/qcom-spmi-sdam.c
index 9aa8f42faa4c..ac7e3b84b2ac 100644
--- a/drivers/nvmem/qcom-spmi-sdam.c
+++ b/drivers/nvmem/qcom-spmi-sdam.c
@@ -60,8 +60,8 @@ static bool sdam_is_ro(unsigned int offset, size_t len)
 	return false;
 }
 
-static int sdam_read(void *priv, unsigned int offset, void *val,
-				size_t bytes)
+static ssize_t sdam_read(void *priv, unsigned int offset, void *val,
+			 size_t bytes)
 {
 	struct sdam_chip *sdam = priv;
 	struct device *dev = sdam->sdam_config.dev;
@@ -78,11 +78,11 @@ static int sdam_read(void *priv, unsigned int offset, void *val,
 		dev_err(dev, "Failed to read SDAM offset %#x len=%zd, rc=%d\n",
 						offset, bytes, rc);
 
-	return rc;
+	return rc < 0 ? rc : bytes;
 }
 
-static int sdam_write(void *priv, unsigned int offset, void *val,
-				size_t bytes)
+static ssize_t sdam_write(void *priv, unsigned int offset, void *val,
+			  size_t bytes)
 {
 	struct sdam_chip *sdam = priv;
 	struct device *dev = sdam->sdam_config.dev;
@@ -105,7 +105,7 @@ static int sdam_write(void *priv, unsigned int offset, void *val,
 		dev_err(dev, "Failed to write SDAM offset %#x len=%zd, rc=%d\n",
 						offset, bytes, rc);
 
-	return rc;
+	return rc < 0 ? rc : bytes;
 }
 
 static int sdam_probe(struct platform_device *pdev)
diff --git a/drivers/nvmem/qfprom.c b/drivers/nvmem/qfprom.c
index 116a39e804c7..4c40c23a92e7 100644
--- a/drivers/nvmem/qfprom.c
+++ b/drivers/nvmem/qfprom.c
@@ -251,10 +251,10 @@ static int qfprom_enable_fuse_blowing(const struct qfprom_priv *priv,
  *
  * Writes to fuses.  WARNING: THIS IS PERMANENT.
  *
- * Return: 0 or -err.
+ * Return: bytes written or -err.
  */
-static int qfprom_reg_write(void *context, unsigned int reg, void *_val,
-			    size_t bytes)
+static ssize_t qfprom_reg_write(void *context, unsigned int reg, void *_val,
+				size_t bytes)
 {
 	struct qfprom_priv *priv = context;
 	struct qfprom_touched_values old;
@@ -314,11 +314,11 @@ static int qfprom_reg_write(void *context, unsigned int reg, void *_val,
 exit_enabled_fuse_blowing:
 	qfprom_disable_fuse_blowing(priv, &old);
 
-	return ret;
+	return ret < 0 ? ret : bytes;
 }
 
-static int qfprom_reg_read(void *context,
-			unsigned int reg, void *_val, size_t bytes)
+static ssize_t qfprom_reg_read(void *context,
+			       unsigned int reg, void *_val, size_t bytes)
 {
 	struct qfprom_priv *priv = context;
 	u8 *val = _val;
@@ -331,7 +331,7 @@ static int qfprom_reg_read(void *context,
 	while (words--)
 		*val++ = readb(base + reg + i++);
 
-	return 0;
+	return bytes;
 }
 
 static void qfprom_runtime_disable(void *data)
diff --git a/drivers/nvmem/qoriq-efuse.c b/drivers/nvmem/qoriq-efuse.c
index e7fd04d6dd94..12a1e9d20e67 100644
--- a/drivers/nvmem/qoriq-efuse.c
+++ b/drivers/nvmem/qoriq-efuse.c
@@ -14,8 +14,8 @@ struct qoriq_efuse_priv {
 	void __iomem *base;
 };
 
-static int qoriq_efuse_read(void *context, unsigned int offset, void *val,
-			    size_t bytes)
+static ssize_t qoriq_efuse_read(void *context, unsigned int offset, void *val,
+				size_t bytes)
 {
 	struct qoriq_efuse_priv *priv = context;
 
@@ -24,7 +24,7 @@ static int qoriq_efuse_read(void *context, unsigned int offset, void *val,
 
 	/* Ignore trailing bytes (there shouldn't be any) */
 
-	return 0;
+	return bytes;
 }
 
 static int qoriq_efuse_probe(struct platform_device *pdev)
diff --git a/drivers/nvmem/rave-sp-eeprom.c b/drivers/nvmem/rave-sp-eeprom.c
index 9ecf3873cbb7..7011b247a96b 100644
--- a/drivers/nvmem/rave-sp-eeprom.c
+++ b/drivers/nvmem/rave-sp-eeprom.c
@@ -214,11 +214,11 @@ rave_sp_eeprom_page_access(struct rave_sp_eeprom *eeprom,
  * arbitrary offset (not necessary page aligned) of arbitrary length
  * (is not constrained by EEPROM page size).
  *
- * Returns zero in case of success or negative error code in case of
- * failure.
+ * Returns number of bytes in case of success or negative error code
+ * in case of failure.
  */
-static int rave_sp_eeprom_access(struct rave_sp_eeprom *eeprom,
-				 enum rave_sp_eeprom_access_type type,
+static ssize_t rave_sp_eeprom_access(struct rave_sp_eeprom *eeprom,
+				     enum rave_sp_eeprom_access_type type,
 				 unsigned int offset, u8 *data,
 				 unsigned int data_len)
 {
@@ -267,18 +267,18 @@ static int rave_sp_eeprom_access(struct rave_sp_eeprom *eeprom,
 	} while (residue);
 out:
 	mutex_unlock(&eeprom->mutex);
-	return ret;
+	return ret < 0 ? ret : data_len;
 }
 
-static int rave_sp_eeprom_reg_read(void *eeprom, unsigned int offset,
-				   void *val, size_t bytes)
+static ssize_t rave_sp_eeprom_reg_read(void *eeprom, unsigned int offset,
+				       void *val, size_t bytes)
 {
 	return rave_sp_eeprom_access(eeprom, RAVE_SP_EEPROM_READ,
 				     offset, val, bytes);
 }
 
-static int rave_sp_eeprom_reg_write(void *eeprom, unsigned int offset,
-				    void *val, size_t bytes)
+static ssize_t rave_sp_eeprom_reg_write(void *eeprom, unsigned int offset,
+					void *val, size_t bytes)
 {
 	return rave_sp_eeprom_access(eeprom, RAVE_SP_EEPROM_WRITE,
 				     offset, val, bytes);
diff --git a/drivers/nvmem/rmem.c b/drivers/nvmem/rmem.c
index 752d0bf4445e..e8526438ce4a 100644
--- a/drivers/nvmem/rmem.c
+++ b/drivers/nvmem/rmem.c
@@ -17,8 +17,8 @@ struct rmem {
 	phys_addr_t size;
 };
 
-static int rmem_read(void *context, unsigned int offset,
-		     void *val, size_t bytes)
+static ssize_t rmem_read(void *context, unsigned int offset,
+			 void *val, size_t bytes)
 {
 	struct rmem *priv = context;
 	size_t available = priv->mem->size;
diff --git a/drivers/nvmem/rockchip-efuse.c b/drivers/nvmem/rockchip-efuse.c
index 2b40978ddb18..36cf62f534df 100644
--- a/drivers/nvmem/rockchip-efuse.c
+++ b/drivers/nvmem/rockchip-efuse.c
@@ -52,8 +52,8 @@ struct rockchip_efuse_chip {
 	struct clk *clk;
 };
 
-static int rockchip_rk3288_efuse_read(void *context, unsigned int offset,
-				      void *val, size_t bytes)
+static ssize_t rockchip_rk3288_efuse_read(void *context, unsigned int offset,
+					  void *val, size_t bytes)
 {
 	struct rockchip_efuse_chip *efuse = context;
 	u8 *buf = val;
@@ -65,6 +65,7 @@ static int rockchip_rk3288_efuse_read(void *context, unsigned int offset,
 		return ret;
 	}
 
+	ret = bytes;
 	writel(RK3288_LOAD | RK3288_PGENB, efuse->base + REG_EFUSE_CTRL);
 	udelay(1);
 	while (bytes--) {
@@ -89,11 +90,11 @@ static int rockchip_rk3288_efuse_read(void *context, unsigned int offset,
 
 	clk_disable_unprepare(efuse->clk);
 
-	return 0;
+	return ret;
 }
 
-static int rockchip_rk3328_efuse_read(void *context, unsigned int offset,
-				      void *val, size_t bytes)
+static ssize_t rockchip_rk3328_efuse_read(void *context, unsigned int offset,
+					  void *val, size_t bytes)
 {
 	struct rockchip_efuse_chip *efuse = context;
 	unsigned int addr_start, addr_end, addr_offset, addr_len;
@@ -144,11 +145,11 @@ static int rockchip_rk3328_efuse_read(void *context, unsigned int offset,
 nomem:
 	clk_disable_unprepare(efuse->clk);
 
-	return ret;
+	return ret < 0 ? ret : bytes;
 }
 
-static int rockchip_rk3399_efuse_read(void *context, unsigned int offset,
-				      void *val, size_t bytes)
+static ssize_t rockchip_rk3399_efuse_read(void *context, unsigned int offset,
+					  void *val, size_t bytes)
 {
 	struct rockchip_efuse_chip *efuse = context;
 	unsigned int addr_start, addr_end, addr_offset, addr_len;
@@ -200,7 +201,7 @@ static int rockchip_rk3399_efuse_read(void *context, unsigned int offset,
 
 	clk_disable_unprepare(efuse->clk);
 
-	return 0;
+	return bytes;
 }
 
 static struct nvmem_config econfig = {
diff --git a/drivers/nvmem/rockchip-otp.c b/drivers/nvmem/rockchip-otp.c
index cb9aa5428350..54c4dbb2e57e 100644
--- a/drivers/nvmem/rockchip-otp.c
+++ b/drivers/nvmem/rockchip-otp.c
@@ -144,10 +144,11 @@ static int rockchip_otp_ecc_enable(struct rockchip_otp *otp, bool enable)
 	return ret;
 }
 
-static int px30_otp_read(void *context, unsigned int offset,
-			 void *val, size_t bytes)
+static ssize_t px30_otp_read(void *context, unsigned int offset,
+			     void *val, size_t bytes)
 {
 	struct rockchip_otp *otp = context;
+	size_t bytes_read = bytes;
 	u8 *buf = val;
 	int ret;
 
@@ -181,11 +182,11 @@ static int px30_otp_read(void *context, unsigned int offset,
 read_end:
 	writel(0x0 | OTPC_USE_USER_MASK, otp->base + OTPC_USER_CTRL);
 
-	return ret;
+	return ret < 0 ? ret : bytes_read;
 }
 
-static int rk3588_otp_read(void *context, unsigned int offset,
-			   void *val, size_t bytes)
+static ssize_t rk3588_otp_read(void *context, unsigned int offset,
+			       void *val, size_t bytes)
 {
 	struct rockchip_otp *otp = context;
 	unsigned int addr_start, addr_end, addr_len;
@@ -227,11 +228,11 @@ static int rk3588_otp_read(void *context, unsigned int offset,
 read_end:
 	kfree(buf);
 
-	return ret;
+	return ret < 0 ? ret : bytes;
 }
 
-static int rockchip_otp_read(void *context, unsigned int offset,
-			     void *val, size_t bytes)
+static ssize_t rockchip_otp_read(void *context, unsigned int offset,
+				 void *val, size_t bytes)
 {
 	struct rockchip_otp *otp = context;
 	int ret;
@@ -249,7 +250,7 @@ static int rockchip_otp_read(void *context, unsigned int offset,
 
 	clk_bulk_disable_unprepare(otp->data->num_clks, otp->clks);
 
-	return ret;
+	return ret < 0 ? ret : bytes;
 }
 
 static struct nvmem_config otp_config = {
diff --git a/drivers/nvmem/sc27xx-efuse.c b/drivers/nvmem/sc27xx-efuse.c
index 4e2ffefac96c..45a2da241271 100644
--- a/drivers/nvmem/sc27xx-efuse.c
+++ b/drivers/nvmem/sc27xx-efuse.c
@@ -121,7 +121,7 @@ static int sc27xx_efuse_poll_status(struct sc27xx_efuse *efuse, u32 bits)
 	return 0;
 }
 
-static int sc27xx_efuse_read(void *context, u32 offset, void *val, size_t bytes)
+static ssize_t sc27xx_efuse_read(void *context, u32 offset, void *val, size_t bytes)
 {
 	struct sc27xx_efuse *efuse = context;
 	u32 buf, blk_index = offset / SC27XX_EFUSE_BLOCK_WIDTH;
@@ -194,6 +194,7 @@ static int sc27xx_efuse_read(void *context, u32 offset, void *val, size_t bytes)
 	if (!ret) {
 		buf >>= blk_offset;
 		memcpy(val, &buf, bytes);
+		ret = bytes;
 	}
 
 	return ret;
diff --git a/drivers/nvmem/sec-qfprom.c b/drivers/nvmem/sec-qfprom.c
index 19799b3fe00a..dbacaab519e7 100644
--- a/drivers/nvmem/sec-qfprom.c
+++ b/drivers/nvmem/sec-qfprom.c
@@ -20,7 +20,7 @@ struct sec_qfprom {
 	struct device *dev;
 };
 
-static int sec_qfprom_reg_read(void *context, unsigned int reg, void *_val, size_t bytes)
+static ssize_t sec_qfprom_reg_read(void *context, unsigned int reg, void *_val, size_t bytes)
 {
 	struct sec_qfprom *priv = context;
 	unsigned int i;
@@ -40,7 +40,7 @@ static int sec_qfprom_reg_read(void *context, unsigned int reg, void *_val, size
 		val[i] = tmp[reg & 3];
 	}
 
-	return 0;
+	return bytes;
 }
 
 static int sec_qfprom_probe(struct platform_device *pdev)
diff --git a/drivers/nvmem/snvs_lpgpr.c b/drivers/nvmem/snvs_lpgpr.c
index 89c27112320f..6b02d69f7158 100644
--- a/drivers/nvmem/snvs_lpgpr.c
+++ b/drivers/nvmem/snvs_lpgpr.c
@@ -50,8 +50,8 @@ static const struct snvs_lpgpr_cfg snvs_lpgpr_cfg_imx7d = {
 	.size		= 16,
 };
 
-static int snvs_lpgpr_write(void *context, unsigned int offset, void *val,
-			    size_t bytes)
+static ssize_t snvs_lpgpr_write(void *context, unsigned int offset, void *val,
+				size_t bytes)
 {
 	struct snvs_lpgpr_priv *priv = context;
 	const struct snvs_lpgpr_cfg *dcfg = priv->dcfg;
@@ -72,18 +72,23 @@ static int snvs_lpgpr_write(void *context, unsigned int offset, void *val,
 	if (lock_reg & IMX_GPR_HL)
 		return -EPERM;
 
-	return regmap_bulk_write(priv->regmap, dcfg->offset + offset, val,
+	ret = regmap_bulk_write(priv->regmap, dcfg->offset + offset, val,
 				bytes / 4);
+
+	return ret < 0 ? ret : bytes;
 }
 
-static int snvs_lpgpr_read(void *context, unsigned int offset, void *val,
-			   size_t bytes)
+static ssize_t snvs_lpgpr_read(void *context, unsigned int offset, void *val,
+			       size_t bytes)
 {
 	struct snvs_lpgpr_priv *priv = context;
 	const struct snvs_lpgpr_cfg *dcfg = priv->dcfg;
+	int ret;
 
-	return regmap_bulk_read(priv->regmap, dcfg->offset + offset,
+	ret = regmap_bulk_read(priv->regmap, dcfg->offset + offset,
 			       val, bytes / 4);
+
+	return ret < 0 ? ret : bytes;
 }
 
 static int snvs_lpgpr_probe(struct platform_device *pdev)
diff --git a/drivers/nvmem/sprd-efuse.c b/drivers/nvmem/sprd-efuse.c
index 1a7e4e5d8b86..54f1e210d3d4 100644
--- a/drivers/nvmem/sprd-efuse.c
+++ b/drivers/nvmem/sprd-efuse.c
@@ -291,7 +291,7 @@ static int sprd_efuse_raw_read(struct sprd_efuse *efuse, int blk, u32 *val,
 	return 0;
 }
 
-static int sprd_efuse_read(void *context, u32 offset, void *val, size_t bytes)
+static ssize_t sprd_efuse_read(void *context, u32 offset, void *val, size_t bytes)
 {
 	struct sprd_efuse *efuse = context;
 	bool blk_double = efuse->data->blk_double;
@@ -318,10 +318,10 @@ static int sprd_efuse_read(void *context, u32 offset, void *val, size_t bytes)
 
 unlock:
 	sprd_efuse_unlock(efuse);
-	return ret;
+	return ret < 0 ? ret : bytes;
 }
 
-static int sprd_efuse_write(void *context, u32 offset, void *val, size_t bytes)
+static ssize_t sprd_efuse_write(void *context, u32 offset, void *val, size_t bytes)
 {
 	struct sprd_efuse *efuse = context;
 	bool blk_double = efuse->data->blk_double;
@@ -355,7 +355,7 @@ static int sprd_efuse_write(void *context, u32 offset, void *val, size_t bytes)
 
 unlock:
 	sprd_efuse_unlock(efuse);
-	return ret;
+	return ret < 0 ? ret : bytes;
 }
 
 static int sprd_efuse_probe(struct platform_device *pdev)
diff --git a/drivers/nvmem/stm32-bsec-optee-ta.c b/drivers/nvmem/stm32-bsec-optee-ta.c
index f89ce791dd12..d2a93bfe80e5 100644
--- a/drivers/nvmem/stm32-bsec-optee-ta.c
+++ b/drivers/nvmem/stm32-bsec-optee-ta.c
@@ -136,8 +136,8 @@ void stm32_bsec_optee_ta_close(void *ctx)
 }
 
 /* stm32_bsec_optee_ta_read() - nvmem read access using PTA client driver */
-int stm32_bsec_optee_ta_read(struct tee_context *ctx, unsigned int offset,
-			     void *buf, size_t bytes)
+ssize_t stm32_bsec_optee_ta_read(struct tee_context *ctx, unsigned int offset,
+				 void *buf, size_t bytes)
 {
 	struct tee_shm *shm;
 	struct tee_ioctl_invoke_arg arg;
@@ -198,12 +198,12 @@ int stm32_bsec_optee_ta_read(struct tee_context *ctx, unsigned int offset,
 out_tee_session:
 	stm32_bsec_ta_close_session(ctx, session_id);
 
-	return ret;
+	return ret < 0 ? ret : bytes;
 }
 
 /* stm32_bsec_optee_ta_write() - nvmem write access using PTA client driver */
-int stm32_bsec_optee_ta_write(struct tee_context *ctx, unsigned int lower,
-			      unsigned int offset, void *buf, size_t bytes)
+ssize_t stm32_bsec_optee_ta_write(struct tee_context *ctx, unsigned int lower,
+				  unsigned int offset, void *buf, size_t bytes)
 {	struct tee_shm *shm;
 	struct tee_ioctl_invoke_arg arg;
 	struct tee_param param[2];
@@ -294,5 +294,5 @@ int stm32_bsec_optee_ta_write(struct tee_context *ctx, unsigned int lower,
 out_tee_session:
 	stm32_bsec_ta_close_session(ctx, session_id);
 
-	return ret;
+	return ret < 0 ? ret : bytes;
 }
diff --git a/drivers/nvmem/stm32-bsec-optee-ta.h b/drivers/nvmem/stm32-bsec-optee-ta.h
index 3966a0535179..c96cfde9b0f0 100644
--- a/drivers/nvmem/stm32-bsec-optee-ta.h
+++ b/drivers/nvmem/stm32-bsec-optee-ta.h
@@ -33,10 +33,10 @@ void stm32_bsec_optee_ta_close(void *ctx);
  * @bytes: number of bytes to read
  *
  * Return:
- *	On success, 0. On failure, -errno.
+ *	On success, bytes read. On failure, -errno.
  */
-int stm32_bsec_optee_ta_read(struct tee_context *ctx, unsigned int offset,
-			     void *buf, size_t bytes);
+ssize_t stm32_bsec_optee_ta_read(struct tee_context *ctx, unsigned int offset,
+				 void *buf, size_t bytes);
 
 /**
  * stm32_bsec_optee_ta_write() - nvmem write access using TA client driver
@@ -47,10 +47,10 @@ int stm32_bsec_optee_ta_read(struct tee_context *ctx, unsigned int offset,
  * @bytes: number of bytes to write
  *
  * Return:
- *	On success, 0. On failure, -errno.
+ *	On success, bytes written. On failure, -errno.
  */
-int stm32_bsec_optee_ta_write(struct tee_context *ctx, unsigned int lower,
-			      unsigned int offset, void *buf, size_t bytes);
+ssize_t stm32_bsec_optee_ta_write(struct tee_context *ctx, unsigned int lower,
+				  unsigned int offset, void *buf, size_t bytes);
 
 #else
 
@@ -63,15 +63,15 @@ static inline void stm32_bsec_optee_ta_close(void *ctx)
 {
 }
 
-static inline int stm32_bsec_optee_ta_read(struct tee_context *ctx,
-					   unsigned int offset, void *buf,
+static inline ssize_t stm32_bsec_optee_ta_read(struct tee_context *ctx,
+					       unsigned int offset, void *buf,
 					   size_t bytes)
 {
 	return -EOPNOTSUPP;
 }
 
-static inline int stm32_bsec_optee_ta_write(struct tee_context *ctx,
-					    unsigned int lower,
+static inline ssize_t stm32_bsec_optee_ta_write(struct tee_context *ctx,
+						unsigned int lower,
 					    unsigned int offset, void *buf,
 					    size_t bytes)
 {
diff --git a/drivers/nvmem/stm32-romem.c b/drivers/nvmem/stm32-romem.c
index 82879b1c9eb9..aed620af788c 100644
--- a/drivers/nvmem/stm32-romem.c
+++ b/drivers/nvmem/stm32-romem.c
@@ -40,8 +40,8 @@ struct stm32_romem_priv {
 	struct tee_context *ctx;
 };
 
-static int stm32_romem_read(void *context, unsigned int offset, void *buf,
-			    size_t bytes)
+static ssize_t stm32_romem_read(void *context, unsigned int offset, void *buf,
+				size_t bytes)
 {
 	struct stm32_romem_priv *priv = context;
 	u8 *buf8 = buf;
@@ -50,7 +50,7 @@ static int stm32_romem_read(void *context, unsigned int offset, void *buf,
 	for (i = offset; i < offset + bytes; i++)
 		*buf8++ = readb_relaxed(priv->base + i);
 
-	return 0;
+	return bytes;
 }
 
 static int stm32_bsec_smc(u8 op, u32 otp, u32 data, u32 *result)
@@ -71,8 +71,8 @@ static int stm32_bsec_smc(u8 op, u32 otp, u32 data, u32 *result)
 #endif
 }
 
-static int stm32_bsec_read(void *context, unsigned int offset, void *buf,
-			   size_t bytes)
+static ssize_t stm32_bsec_read(void *context, unsigned int offset, void *buf,
+			       size_t bytes)
 {
 	struct stm32_romem_priv *priv = context;
 	struct device *dev = priv->cfg.dev;
@@ -115,11 +115,11 @@ static int stm32_bsec_read(void *context, unsigned int offset, void *buf,
 		skip_bytes = 0;
 	}
 
-	return 0;
+	return j;
 }
 
-static int stm32_bsec_write(void *context, unsigned int offset, void *buf,
-			    size_t bytes)
+static ssize_t stm32_bsec_write(void *context, unsigned int offset, void *buf,
+				size_t bytes)
 {
 	struct stm32_romem_priv *priv = context;
 	struct device *dev = priv->cfg.dev;
@@ -142,19 +142,19 @@ static int stm32_bsec_write(void *context, unsigned int offset, void *buf,
 	if (offset + bytes >= priv->lower * 4)
 		dev_warn(dev, "Update of upper OTPs with ECC protection (word programming, only once)\n");
 
-	return 0;
+	return bytes;
 }
 
-static int stm32_bsec_pta_read(void *context, unsigned int offset, void *buf,
-			       size_t bytes)
+static ssize_t stm32_bsec_pta_read(void *context, unsigned int offset, void *buf,
+				   size_t bytes)
 {
 	struct stm32_romem_priv *priv = context;
 
 	return stm32_bsec_optee_ta_read(priv->ctx, offset, buf, bytes);
 }
 
-static int stm32_bsec_pta_write(void *context, unsigned int offset, void *buf,
-				size_t bytes)
+static ssize_t stm32_bsec_pta_write(void *context, unsigned int offset, void *buf,
+				    size_t bytes)
 {
 	struct stm32_romem_priv *priv = context;
 
diff --git a/drivers/nvmem/sunplus-ocotp.c b/drivers/nvmem/sunplus-ocotp.c
index 38f5d9df39cd..7bda128bb93e 100644
--- a/drivers/nvmem/sunplus-ocotp.c
+++ b/drivers/nvmem/sunplus-ocotp.c
@@ -114,7 +114,7 @@ static int sp_otp_read_real(struct sp_ocotp_priv *otp, int addr, char *value)
 	return ret;
 }
 
-static int sp_ocotp_read(void *priv, unsigned int offset, void *value, size_t bytes)
+static ssize_t sp_ocotp_read(void *priv, unsigned int offset, void *value, size_t bytes)
 {
 	struct sp_ocotp_priv *otp = priv;
 	unsigned int addr;
@@ -140,7 +140,7 @@ static int sp_ocotp_read(void *priv, unsigned int offset, void *value, size_t by
 disable_clk:
 	clk_disable(otp->clk);
 
-	return ret;
+	return ret < 0 ? ret : bytes;
 }
 
 static struct nvmem_config sp_ocotp_nvmem_config = {
diff --git a/drivers/nvmem/sunxi_sid.c b/drivers/nvmem/sunxi_sid.c
index ba14a76208ab..0133263d2adb 100644
--- a/drivers/nvmem/sunxi_sid.c
+++ b/drivers/nvmem/sunxi_sid.c
@@ -36,8 +36,8 @@ struct sunxi_sid {
 	u32			value_offset;
 };
 
-static int sunxi_sid_read(void *context, unsigned int offset,
-			  void *val, size_t bytes)
+static ssize_t sunxi_sid_read(void *context, unsigned int offset,
+			      void *val, size_t bytes)
 {
 	struct sunxi_sid *sid = context;
 	u32 word;
@@ -56,7 +56,7 @@ static int sunxi_sid_read(void *context, unsigned int offset,
 	word = readl_relaxed(sid->base + sid->value_offset + offset);
 	memcpy(val, &word, bytes);
 
-	return 0;
+	return bytes;
 }
 
 static int sun8i_sid_register_readout(const struct sunxi_sid *sid,
@@ -90,10 +90,11 @@ static int sun8i_sid_register_readout(const struct sunxi_sid *sid,
  * to be not reliable at all.
  * Read by the registers instead.
  */
-static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
-				 void *val, size_t bytes)
+static ssize_t sun8i_sid_read_by_reg(void *context, unsigned int offset,
+				     void *val, size_t bytes)
 {
 	struct sunxi_sid *sid = context;
+	size_t bytes_read = bytes;
 	u32 word;
 	int ret;
 
@@ -109,7 +110,7 @@ static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
 	}
 
 	if (!bytes)
-		return 0;
+		return bytes_read;
 
 	/* Handle any trailing bytes */
 	ret = sun8i_sid_register_readout(sid, offset, &word);
@@ -118,7 +119,7 @@ static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
 
 	memcpy(val, &word, bytes);
 
-	return 0;
+	return bytes_read;
 }
 
 static int sunxi_sid_probe(struct platform_device *pdev)
diff --git a/drivers/nvmem/u-boot-env.c b/drivers/nvmem/u-boot-env.c
index befbab156cda..2288a2891bb2 100644
--- a/drivers/nvmem/u-boot-env.c
+++ b/drivers/nvmem/u-boot-env.c
@@ -47,8 +47,8 @@ struct u_boot_env_image_broadcom {
 	DECLARE_FLEX_ARRAY(uint8_t, data);
 } __packed;
 
-static int u_boot_env_read(void *context, unsigned int offset, void *val,
-			   size_t bytes)
+static ssize_t u_boot_env_read(void *context, unsigned int offset, void *val,
+			       size_t bytes)
 {
 	struct u_boot_env *priv = context;
 	struct device *dev = priv->dev;
@@ -66,7 +66,7 @@ static int u_boot_env_read(void *context, unsigned int offset, void *val,
 		return -EIO;
 	}
 
-	return 0;
+	return bytes_read;
 }
 
 static int u_boot_env_read_post_process_ethaddr(void *context, const char *id, int index,
diff --git a/drivers/nvmem/uniphier-efuse.c b/drivers/nvmem/uniphier-efuse.c
index 6ad3295d3195..a6c28e03adc2 100644
--- a/drivers/nvmem/uniphier-efuse.c
+++ b/drivers/nvmem/uniphier-efuse.c
@@ -16,8 +16,8 @@ struct uniphier_efuse_priv {
 	void __iomem *base;
 };
 
-static int uniphier_reg_read(void *context,
-			     unsigned int reg, void *_val, size_t bytes)
+static ssize_t uniphier_reg_read(void *context,
+				 unsigned int reg, void *_val, size_t bytes)
 {
 	struct uniphier_efuse_priv *priv = context;
 	u8 *val = _val;
@@ -26,7 +26,7 @@ static int uniphier_reg_read(void *context,
 	for (offs = 0; offs < bytes; offs += sizeof(u8))
 		*val++ = readb(priv->base + reg + offs);
 
-	return 0;
+	return bytes;
 }
 
 static int uniphier_efuse_probe(struct platform_device *pdev)
diff --git a/drivers/nvmem/vf610-ocotp.c b/drivers/nvmem/vf610-ocotp.c
index ee9c61ae727d..4e2bdb38305d 100644
--- a/drivers/nvmem/vf610-ocotp.c
+++ b/drivers/nvmem/vf610-ocotp.c
@@ -143,11 +143,12 @@ static int vf610_get_fuse_address(int base_addr_offset)
 	return -EINVAL;
 }
 
-static int vf610_ocotp_read(void *context, unsigned int offset,
-			void *val, size_t bytes)
+static ssize_t vf610_ocotp_read(void *context, unsigned int offset,
+				void *val, size_t bytes)
 {
 	struct vf610_ocotp *ocotp = context;
 	void __iomem *base = ocotp->base;
+	size_t bytes_read = bytes;
 	u32 reg, *buf = val;
 	int fuse_addr;
 	int ret;
@@ -193,7 +194,7 @@ static int vf610_ocotp_read(void *context, unsigned int offset,
 		offset += 4;
 	}
 
-	return 0;
+	return bytes_read;
 }
 
 static struct nvmem_config ocotp_config = {
diff --git a/drivers/nvmem/zynqmp_nvmem.c b/drivers/nvmem/zynqmp_nvmem.c
index 8682adaacd69..1502d4998159 100644
--- a/drivers/nvmem/zynqmp_nvmem.c
+++ b/drivers/nvmem/zynqmp_nvmem.c
@@ -56,8 +56,8 @@ struct xilinx_efuse {
 	u32 pufuserfuse;
 };
 
-static int zynqmp_efuse_access(void *context, unsigned int offset,
-			       void *val, size_t bytes, enum efuse_access flag,
+static ssize_t zynqmp_efuse_access(void *context, unsigned int offset,
+				   void *val, size_t bytes, enum efuse_access flag,
 			       unsigned int pufflag)
 {
 	struct device *dev = context;
@@ -140,10 +140,10 @@ static int zynqmp_efuse_access(void *context, unsigned int offset,
 	dma_free_coherent(dev, sizeof(struct xilinx_efuse),
 			  efuse, dma_addr);
 
-	return ret;
+	return ret < 0 ? ret : bytes;
 }
 
-static int zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size_t bytes)
+static ssize_t zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size_t bytes)
 {
 	struct device *dev = context;
 	int ret;
@@ -166,6 +166,7 @@ static int zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size
 
 		dev_dbg(dev, "Read chipid val %x %x\n", idcode, version);
 		*(int *)val = version & SILICON_REVISION_MASK;
+		ret = SOC_VER_SIZE;
 		break;
 	/* Efuse offset starts from 0xc */
 	case EFUSE_START_OFFSET ... EFUSE_END_OFFSET:
@@ -182,8 +183,8 @@ static int zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size
 	return ret;
 }
 
-static int zynqmp_nvmem_write(void *context,
-			      unsigned int offset, void *val, size_t bytes)
+static ssize_t zynqmp_nvmem_write(void *context,
+				  unsigned int offset, void *val, size_t bytes)
 {
 	int pufflag = 0;
 
diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
index 3ebeaa0ded00..f7e83a59aa2f 100644
--- a/include/linux/nvmem-provider.h
+++ b/include/linux/nvmem-provider.h
@@ -16,9 +16,9 @@
 #include <linux/gpio/consumer.h>
 
 struct nvmem_device;
-typedef int (*nvmem_reg_read_t)(void *priv, unsigned int offset,
+typedef ssize_t (*nvmem_reg_read_t)(void *priv, unsigned int offset,
 				void *val, size_t bytes);
-typedef int (*nvmem_reg_write_t)(void *priv, unsigned int offset,
+typedef ssize_t (*nvmem_reg_write_t)(void *priv, unsigned int offset,
 				 void *val, size_t bytes);
 /* used for vendor specific post processing of cell data */
 typedef int (*nvmem_cell_post_process_t)(void *priv, const char *id, int index,
-- 
2.44.0.769.g3c40516874-goog

Re: [PATCH v2 1/1] nvmem: Change return type of reg read/write to ssize_t

[Andre Przywara]

On Wed, 24 Apr 2024 07:42:42 +0000
Joy Chakraborty <joychakr@google.com> wrote:

> Change return type of reg_read() and reg_write() callback to ssize_t for
> nvmem suppliers to return number of bytes read/written to the nvmem core.
> 
> Currently nvmem core assumes the amount of data read/written is equal
> to what it has requested from the supplier, this return code facilitates
> better error handling in the nvmem core.
> 
> Signed-off-by: Joy Chakraborty <joychakr@google.com>

There are two problems in the sunxi driver:

> ---
>  drivers/nvmem/apple-efuses.c        |  7 +--
>  drivers/nvmem/bcm-ocotp.c           | 12 ++---
>  drivers/nvmem/brcm_nvram.c          | 10 ++--
>  drivers/nvmem/core.c                | 83 +++++++++++++----------------
>  drivers/nvmem/imx-iim.c             |  6 +--
>  drivers/nvmem/imx-ocotp-ele.c       |  4 +-
>  drivers/nvmem/imx-ocotp-scu.c       | 12 ++---
>  drivers/nvmem/imx-ocotp.c           | 10 ++--
>  drivers/nvmem/jz4780-efuse.c        |  7 +--
>  drivers/nvmem/lan9662-otpc.c        | 12 ++---
>  drivers/nvmem/layerscape-sfp.c      | 11 ++--
>  drivers/nvmem/lpc18xx_eeprom.c      | 14 ++---
>  drivers/nvmem/lpc18xx_otp.c         |  6 +--
>  drivers/nvmem/meson-efuse.c         | 22 +++++---
>  drivers/nvmem/meson-mx-efuse.c      |  6 +--
>  drivers/nvmem/microchip-otpc.c      |  6 +--
>  drivers/nvmem/mtk-efuse.c           |  6 +--
>  drivers/nvmem/mxs-ocotp.c           |  7 +--
>  drivers/nvmem/nintendo-otp.c        |  6 +--
>  drivers/nvmem/qcom-spmi-sdam.c      | 12 ++---
>  drivers/nvmem/qfprom.c              | 14 ++---
>  drivers/nvmem/qoriq-efuse.c         |  6 +--
>  drivers/nvmem/rave-sp-eeprom.c      | 18 +++----
>  drivers/nvmem/rmem.c                |  4 +-
>  drivers/nvmem/rockchip-efuse.c      | 19 +++----
>  drivers/nvmem/rockchip-otp.c        | 19 +++----
>  drivers/nvmem/sc27xx-efuse.c        |  3 +-
>  drivers/nvmem/sec-qfprom.c          |  4 +-
>  drivers/nvmem/snvs_lpgpr.c          | 17 +++---
>  drivers/nvmem/sprd-efuse.c          |  8 +--
>  drivers/nvmem/stm32-bsec-optee-ta.c | 12 ++---
>  drivers/nvmem/stm32-bsec-optee-ta.h | 20 +++----
>  drivers/nvmem/stm32-romem.c         | 26 ++++-----
>  drivers/nvmem/sunplus-ocotp.c       |  4 +-
>  drivers/nvmem/sunxi_sid.c           | 15 +++---
>  drivers/nvmem/u-boot-env.c          |  6 +--
>  drivers/nvmem/uniphier-efuse.c      |  6 +--
>  drivers/nvmem/vf610-ocotp.c         |  7 +--
>  drivers/nvmem/zynqmp_nvmem.c        | 13 ++---
>  include/linux/nvmem-provider.h      |  4 +-
>  40 files changed, 253 insertions(+), 231 deletions(-)

[ ... ]

> 
> diff --git a/drivers/nvmem/sunxi_sid.c b/drivers/nvmem/sunxi_sid.c
> index ba14a76208ab..0133263d2adb 100644
> --- a/drivers/nvmem/sunxi_sid.c
> +++ b/drivers/nvmem/sunxi_sid.c
> @@ -36,8 +36,8 @@ struct sunxi_sid {
>  	u32			value_offset;
>  };
>  
> -static int sunxi_sid_read(void *context, unsigned int offset,
> -			  void *val, size_t bytes)
> +static ssize_t sunxi_sid_read(void *context, unsigned int offset,
> +			      void *val, size_t bytes)
>  {
>  	struct sunxi_sid *sid = context;
>  	u32 word;
> @@ -56,7 +56,7 @@ static int sunxi_sid_read(void *context, unsigned int offset,

	(adding more context here)

>
>	val += round_down(bytes, 4);
>	offset += round_down(bytes, 4);
>	bytes = bytes % 4;
>
>	if (!bytes)
>		return 0;
>
>	/* Handle any trailing bytes */
>  	word = readl_relaxed(sid->base + sid->value_offset + offset);
>  	memcpy(val, &word, bytes);
>  
> -	return 0;
> +	return bytes;

So this is only the code path in case the read request was not 4 byte
aligned, so the "return 0;" above must also be changed. But please note
that the bytes parameter is changed, so we either need to save that, or
derive the amount read from something else.

Cheers,
Andre

>  }
>  
>  static int sun8i_sid_register_readout(const struct sunxi_sid *sid,
> @@ -90,10 +90,11 @@ static int sun8i_sid_register_readout(const struct sunxi_sid *sid,
>   * to be not reliable at all.
>   * Read by the registers instead.
>   */
> -static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
> -				 void *val, size_t bytes)
> +static ssize_t sun8i_sid_read_by_reg(void *context, unsigned int offset,
> +				     void *val, size_t bytes)
>  {
>  	struct sunxi_sid *sid = context;
> +	size_t bytes_read = bytes;
>  	u32 word;
>  	int ret;
>  
> @@ -109,7 +110,7 @@ static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
>  	}
>  
>  	if (!bytes)
> -		return 0;
> +		return bytes_read;
>  
>  	/* Handle any trailing bytes */
>  	ret = sun8i_sid_register_readout(sid, offset, &word);
> @@ -118,7 +119,7 @@ static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
>  
>  	memcpy(val, &word, bytes);
>  
> -	return 0;
> +	return bytes_read;
>  }
>  
>  static int sunxi_sid_probe(struct platform_device *pdev)
> diff --git a/drivers/nvmem/u-boot-env.c b/drivers/nvmem/u-boot-env.c
> index befbab156cda..2288a2891bb2 100644
> --- a/drivers/nvmem/u-boot-env.c
> +++ b/drivers/nvmem/u-boot-env.c
> @@ -47,8 +47,8 @@ struct u_boot_env_image_broadcom {
>  	DECLARE_FLEX_ARRAY(uint8_t, data);
>  } __packed;
>  
> -static int u_boot_env_read(void *context, unsigned int offset, void *val,
> -			   size_t bytes)
> +static ssize_t u_boot_env_read(void *context, unsigned int offset, void *val,
> +			       size_t bytes)
>  {
>  	struct u_boot_env *priv = context;
>  	struct device *dev = priv->dev;
> @@ -66,7 +66,7 @@ static int u_boot_env_read(void *context, unsigned int offset, void *val,
>  		return -EIO;
>  	}
>  
> -	return 0;
> +	return bytes_read;
>  }
>  
>  static int u_boot_env_read_post_process_ethaddr(void *context, const char *id, int index,
> diff --git a/drivers/nvmem/uniphier-efuse.c b/drivers/nvmem/uniphier-efuse.c
> index 6ad3295d3195..a6c28e03adc2 100644
> --- a/drivers/nvmem/uniphier-efuse.c
> +++ b/drivers/nvmem/uniphier-efuse.c
> @@ -16,8 +16,8 @@ struct uniphier_efuse_priv {
>  	void __iomem *base;
>  };
>  
> -static int uniphier_reg_read(void *context,
> -			     unsigned int reg, void *_val, size_t bytes)
> +static ssize_t uniphier_reg_read(void *context,
> +				 unsigned int reg, void *_val, size_t bytes)
>  {
>  	struct uniphier_efuse_priv *priv = context;
>  	u8 *val = _val;
> @@ -26,7 +26,7 @@ static int uniphier_reg_read(void *context,
>  	for (offs = 0; offs < bytes; offs += sizeof(u8))
>  		*val++ = readb(priv->base + reg + offs);
>  
> -	return 0;
> +	return bytes;
>  }
>  
>  static int uniphier_efuse_probe(struct platform_device *pdev)
> diff --git a/drivers/nvmem/vf610-ocotp.c b/drivers/nvmem/vf610-ocotp.c
> index ee9c61ae727d..4e2bdb38305d 100644
> --- a/drivers/nvmem/vf610-ocotp.c
> +++ b/drivers/nvmem/vf610-ocotp.c
> @@ -143,11 +143,12 @@ static int vf610_get_fuse_address(int base_addr_offset)
>  	return -EINVAL;
>  }
>  
> -static int vf610_ocotp_read(void *context, unsigned int offset,
> -			void *val, size_t bytes)
> +static ssize_t vf610_ocotp_read(void *context, unsigned int offset,
> +				void *val, size_t bytes)
>  {
>  	struct vf610_ocotp *ocotp = context;
>  	void __iomem *base = ocotp->base;
> +	size_t bytes_read = bytes;
>  	u32 reg, *buf = val;
>  	int fuse_addr;
>  	int ret;
> @@ -193,7 +194,7 @@ static int vf610_ocotp_read(void *context, unsigned int offset,
>  		offset += 4;
>  	}
>  
> -	return 0;
> +	return bytes_read;
>  }
>  
>  static struct nvmem_config ocotp_config = {
> diff --git a/drivers/nvmem/zynqmp_nvmem.c b/drivers/nvmem/zynqmp_nvmem.c
> index 8682adaacd69..1502d4998159 100644
> --- a/drivers/nvmem/zynqmp_nvmem.c
> +++ b/drivers/nvmem/zynqmp_nvmem.c
> @@ -56,8 +56,8 @@ struct xilinx_efuse {
>  	u32 pufuserfuse;
>  };
>  
> -static int zynqmp_efuse_access(void *context, unsigned int offset,
> -			       void *val, size_t bytes, enum efuse_access flag,
> +static ssize_t zynqmp_efuse_access(void *context, unsigned int offset,
> +				   void *val, size_t bytes, enum efuse_access flag,
>  			       unsigned int pufflag)
>  {
>  	struct device *dev = context;
> @@ -140,10 +140,10 @@ static int zynqmp_efuse_access(void *context, unsigned int offset,
>  	dma_free_coherent(dev, sizeof(struct xilinx_efuse),
>  			  efuse, dma_addr);
>  
> -	return ret;
> +	return ret < 0 ? ret : bytes;
>  }
>  
> -static int zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size_t bytes)
> +static ssize_t zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size_t bytes)
>  {
>  	struct device *dev = context;
>  	int ret;
> @@ -166,6 +166,7 @@ static int zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size
>  
>  		dev_dbg(dev, "Read chipid val %x %x\n", idcode, version);
>  		*(int *)val = version & SILICON_REVISION_MASK;
> +		ret = SOC_VER_SIZE;
>  		break;
>  	/* Efuse offset starts from 0xc */
>  	case EFUSE_START_OFFSET ... EFUSE_END_OFFSET:
> @@ -182,8 +183,8 @@ static int zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size
>  	return ret;
>  }
>  
> -static int zynqmp_nvmem_write(void *context,
> -			      unsigned int offset, void *val, size_t bytes)
> +static ssize_t zynqmp_nvmem_write(void *context,
> +				  unsigned int offset, void *val, size_t bytes)
>  {
>  	int pufflag = 0;
>  
> diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
> index 3ebeaa0ded00..f7e83a59aa2f 100644
> --- a/include/linux/nvmem-provider.h
> +++ b/include/linux/nvmem-provider.h
> @@ -16,9 +16,9 @@
>  #include <linux/gpio/consumer.h>
>  
>  struct nvmem_device;
> -typedef int (*nvmem_reg_read_t)(void *priv, unsigned int offset,
> +typedef ssize_t (*nvmem_reg_read_t)(void *priv, unsigned int offset,
>  				void *val, size_t bytes);
> -typedef int (*nvmem_reg_write_t)(void *priv, unsigned int offset,
> +typedef ssize_t (*nvmem_reg_write_t)(void *priv, unsigned int offset,
>  				 void *val, size_t bytes);
>  /* used for vendor specific post processing of cell data */
>  typedef int (*nvmem_cell_post_process_t)(void *priv, const char *id, int index,

Re: [PATCH v2 1/1] nvmem: Change return type of reg read/write to ssize_t

[Joy Chakraborty]

On Wed, Apr 24, 2024 at 3:11 PM Andre Przywara <andre.przywara@arm.com> wrote:
>
> On Wed, 24 Apr 2024 07:42:42 +0000
> Joy Chakraborty <joychakr@google.com> wrote:
>
> > Change return type of reg_read() and reg_write() callback to ssize_t for
> > nvmem suppliers to return number of bytes read/written to the nvmem core.
> >
> > Currently nvmem core assumes the amount of data read/written is equal
> > to what it has requested from the supplier, this return code facilitates
> > better error handling in the nvmem core.
> >
> > Signed-off-by: Joy Chakraborty <joychakr@google.com>
>
> There are two problems in the sunxi driver:
>
> > ---
> >  drivers/nvmem/apple-efuses.c        |  7 +--
> >  drivers/nvmem/bcm-ocotp.c           | 12 ++---
> >  drivers/nvmem/brcm_nvram.c          | 10 ++--
> >  drivers/nvmem/core.c                | 83 +++++++++++++----------------
> >  drivers/nvmem/imx-iim.c             |  6 +--
> >  drivers/nvmem/imx-ocotp-ele.c       |  4 +-
> >  drivers/nvmem/imx-ocotp-scu.c       | 12 ++---
> >  drivers/nvmem/imx-ocotp.c           | 10 ++--
> >  drivers/nvmem/jz4780-efuse.c        |  7 +--
> >  drivers/nvmem/lan9662-otpc.c        | 12 ++---
> >  drivers/nvmem/layerscape-sfp.c      | 11 ++--
> >  drivers/nvmem/lpc18xx_eeprom.c      | 14 ++---
> >  drivers/nvmem/lpc18xx_otp.c         |  6 +--
> >  drivers/nvmem/meson-efuse.c         | 22 +++++---
> >  drivers/nvmem/meson-mx-efuse.c      |  6 +--
> >  drivers/nvmem/microchip-otpc.c      |  6 +--
> >  drivers/nvmem/mtk-efuse.c           |  6 +--
> >  drivers/nvmem/mxs-ocotp.c           |  7 +--
> >  drivers/nvmem/nintendo-otp.c        |  6 +--
> >  drivers/nvmem/qcom-spmi-sdam.c      | 12 ++---
> >  drivers/nvmem/qfprom.c              | 14 ++---
> >  drivers/nvmem/qoriq-efuse.c         |  6 +--
> >  drivers/nvmem/rave-sp-eeprom.c      | 18 +++----
> >  drivers/nvmem/rmem.c                |  4 +-
> >  drivers/nvmem/rockchip-efuse.c      | 19 +++----
> >  drivers/nvmem/rockchip-otp.c        | 19 +++----
> >  drivers/nvmem/sc27xx-efuse.c        |  3 +-
> >  drivers/nvmem/sec-qfprom.c          |  4 +-
> >  drivers/nvmem/snvs_lpgpr.c          | 17 +++---
> >  drivers/nvmem/sprd-efuse.c          |  8 +--
> >  drivers/nvmem/stm32-bsec-optee-ta.c | 12 ++---
> >  drivers/nvmem/stm32-bsec-optee-ta.h | 20 +++----
> >  drivers/nvmem/stm32-romem.c         | 26 ++++-----
> >  drivers/nvmem/sunplus-ocotp.c       |  4 +-
> >  drivers/nvmem/sunxi_sid.c           | 15 +++---
> >  drivers/nvmem/u-boot-env.c          |  6 +--
> >  drivers/nvmem/uniphier-efuse.c      |  6 +--
> >  drivers/nvmem/vf610-ocotp.c         |  7 +--
> >  drivers/nvmem/zynqmp_nvmem.c        | 13 ++---
> >  include/linux/nvmem-provider.h      |  4 +-
> >  40 files changed, 253 insertions(+), 231 deletions(-)
>
> [ ... ]
>
> >
> > diff --git a/drivers/nvmem/sunxi_sid.c b/drivers/nvmem/sunxi_sid.c
> > index ba14a76208ab..0133263d2adb 100644
> > --- a/drivers/nvmem/sunxi_sid.c
> > +++ b/drivers/nvmem/sunxi_sid.c
> > @@ -36,8 +36,8 @@ struct sunxi_sid {
> >       u32                     value_offset;
> >  };
> >
> > -static int sunxi_sid_read(void *context, unsigned int offset,
> > -                       void *val, size_t bytes)
> > +static ssize_t sunxi_sid_read(void *context, unsigned int offset,
> > +                           void *val, size_t bytes)
> >  {
> >       struct sunxi_sid *sid = context;
> >       u32 word;
> > @@ -56,7 +56,7 @@ static int sunxi_sid_read(void *context, unsigned int offset,
>
>         (adding more context here)
>
> >
> >       val += round_down(bytes, 4);
> >       offset += round_down(bytes, 4);
> >       bytes = bytes % 4;
> >
> >       if (!bytes)
> >               return 0;
> >
> >       /* Handle any trailing bytes */
> >       word = readl_relaxed(sid->base + sid->value_offset + offset);
> >       memcpy(val, &word, bytes);
> >
> > -     return 0;
> > +     return bytes;
>
> So this is only the code path in case the read request was not 4 byte
> aligned, so the "return 0;" above must also be changed. But please note
> that the bytes parameter is changed, so we either need to save that, or
> derive the amount read from something else.
>
> Cheers,
> Andre

Ack, Missed the return logic above.
Will fix this next version by saving bytes read in another variable.
Thanks for reviewing.

Thanks
Joy

>
> >  }
> >
> >  static int sun8i_sid_register_readout(const struct sunxi_sid *sid,
> > @@ -90,10 +90,11 @@ static int sun8i_sid_register_readout(const struct sunxi_sid *sid,
> >   * to be not reliable at all.
> >   * Read by the registers instead.
> >   */
> > -static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
> > -                              void *val, size_t bytes)
> > +static ssize_t sun8i_sid_read_by_reg(void *context, unsigned int offset,
> > +                                  void *val, size_t bytes)
> >  {
> >       struct sunxi_sid *sid = context;
> > +     size_t bytes_read = bytes;
> >       u32 word;
> >       int ret;
> >
> > @@ -109,7 +110,7 @@ static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
> >       }
> >
> >       if (!bytes)
> > -             return 0;
> > +             return bytes_read;
> >
> >       /* Handle any trailing bytes */
> >       ret = sun8i_sid_register_readout(sid, offset, &word);
> > @@ -118,7 +119,7 @@ static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
> >
> >       memcpy(val, &word, bytes);
> >
> > -     return 0;
> > +     return bytes_read;
> >  }
> >
> >  static int sunxi_sid_probe(struct platform_device *pdev)
> > diff --git a/drivers/nvmem/u-boot-env.c b/drivers/nvmem/u-boot-env.c
> > index befbab156cda..2288a2891bb2 100644
> > --- a/drivers/nvmem/u-boot-env.c
> > +++ b/drivers/nvmem/u-boot-env.c
> > @@ -47,8 +47,8 @@ struct u_boot_env_image_broadcom {
> >       DECLARE_FLEX_ARRAY(uint8_t, data);
> >  } __packed;
> >
> > -static int u_boot_env_read(void *context, unsigned int offset, void *val,
> > -                        size_t bytes)
> > +static ssize_t u_boot_env_read(void *context, unsigned int offset, void *val,
> > +                            size_t bytes)
> >  {
> >       struct u_boot_env *priv = context;
> >       struct device *dev = priv->dev;
> > @@ -66,7 +66,7 @@ static int u_boot_env_read(void *context, unsigned int offset, void *val,
> >               return -EIO;
> >       }
> >
> > -     return 0;
> > +     return bytes_read;
> >  }
> >
> >  static int u_boot_env_read_post_process_ethaddr(void *context, const char *id, int index,
> > diff --git a/drivers/nvmem/uniphier-efuse.c b/drivers/nvmem/uniphier-efuse.c
> > index 6ad3295d3195..a6c28e03adc2 100644
> > --- a/drivers/nvmem/uniphier-efuse.c
> > +++ b/drivers/nvmem/uniphier-efuse.c
> > @@ -16,8 +16,8 @@ struct uniphier_efuse_priv {
> >       void __iomem *base;
> >  };
> >
> > -static int uniphier_reg_read(void *context,
> > -                          unsigned int reg, void *_val, size_t bytes)
> > +static ssize_t uniphier_reg_read(void *context,
> > +                              unsigned int reg, void *_val, size_t bytes)
> >  {
> >       struct uniphier_efuse_priv *priv = context;
> >       u8 *val = _val;
> > @@ -26,7 +26,7 @@ static int uniphier_reg_read(void *context,
> >       for (offs = 0; offs < bytes; offs += sizeof(u8))
> >               *val++ = readb(priv->base + reg + offs);
> >
> > -     return 0;
> > +     return bytes;
> >  }
> >
> >  static int uniphier_efuse_probe(struct platform_device *pdev)
> > diff --git a/drivers/nvmem/vf610-ocotp.c b/drivers/nvmem/vf610-ocotp.c
> > index ee9c61ae727d..4e2bdb38305d 100644
> > --- a/drivers/nvmem/vf610-ocotp.c
> > +++ b/drivers/nvmem/vf610-ocotp.c
> > @@ -143,11 +143,12 @@ static int vf610_get_fuse_address(int base_addr_offset)
> >       return -EINVAL;
> >  }
> >
> > -static int vf610_ocotp_read(void *context, unsigned int offset,
> > -                     void *val, size_t bytes)
> > +static ssize_t vf610_ocotp_read(void *context, unsigned int offset,
> > +                             void *val, size_t bytes)
> >  {
> >       struct vf610_ocotp *ocotp = context;
> >       void __iomem *base = ocotp->base;
> > +     size_t bytes_read = bytes;
> >       u32 reg, *buf = val;
> >       int fuse_addr;
> >       int ret;
> > @@ -193,7 +194,7 @@ static int vf610_ocotp_read(void *context, unsigned int offset,
> >               offset += 4;
> >       }
> >
> > -     return 0;
> > +     return bytes_read;
> >  }
> >
> >  static struct nvmem_config ocotp_config = {
> > diff --git a/drivers/nvmem/zynqmp_nvmem.c b/drivers/nvmem/zynqmp_nvmem.c
> > index 8682adaacd69..1502d4998159 100644
> > --- a/drivers/nvmem/zynqmp_nvmem.c
> > +++ b/drivers/nvmem/zynqmp_nvmem.c
> > @@ -56,8 +56,8 @@ struct xilinx_efuse {
> >       u32 pufuserfuse;
> >  };
> >
> > -static int zynqmp_efuse_access(void *context, unsigned int offset,
> > -                            void *val, size_t bytes, enum efuse_access flag,
> > +static ssize_t zynqmp_efuse_access(void *context, unsigned int offset,
> > +                                void *val, size_t bytes, enum efuse_access flag,
> >                              unsigned int pufflag)
> >  {
> >       struct device *dev = context;
> > @@ -140,10 +140,10 @@ static int zynqmp_efuse_access(void *context, unsigned int offset,
> >       dma_free_coherent(dev, sizeof(struct xilinx_efuse),
> >                         efuse, dma_addr);
> >
> > -     return ret;
> > +     return ret < 0 ? ret : bytes;
> >  }
> >
> > -static int zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size_t bytes)
> > +static ssize_t zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size_t bytes)
> >  {
> >       struct device *dev = context;
> >       int ret;
> > @@ -166,6 +166,7 @@ static int zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size
> >
> >               dev_dbg(dev, "Read chipid val %x %x\n", idcode, version);
> >               *(int *)val = version & SILICON_REVISION_MASK;
> > +             ret = SOC_VER_SIZE;
> >               break;
> >       /* Efuse offset starts from 0xc */
> >       case EFUSE_START_OFFSET ... EFUSE_END_OFFSET:
> > @@ -182,8 +183,8 @@ static int zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size
> >       return ret;
> >  }
> >
> > -static int zynqmp_nvmem_write(void *context,
> > -                           unsigned int offset, void *val, size_t bytes)
> > +static ssize_t zynqmp_nvmem_write(void *context,
> > +                               unsigned int offset, void *val, size_t bytes)
> >  {
> >       int pufflag = 0;
> >
> > diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
> > index 3ebeaa0ded00..f7e83a59aa2f 100644
> > --- a/include/linux/nvmem-provider.h
> > +++ b/include/linux/nvmem-provider.h
> > @@ -16,9 +16,9 @@
> >  #include <linux/gpio/consumer.h>
> >
> >  struct nvmem_device;
> > -typedef int (*nvmem_reg_read_t)(void *priv, unsigned int offset,
> > +typedef ssize_t (*nvmem_reg_read_t)(void *priv, unsigned int offset,
> >                               void *val, size_t bytes);
> > -typedef int (*nvmem_reg_write_t)(void *priv, unsigned int offset,
> > +typedef ssize_t (*nvmem_reg_write_t)(void *priv, unsigned int offset,
> >                                void *val, size_t bytes);
> >  /* used for vendor specific post processing of cell data */
> >  typedef int (*nvmem_cell_post_process_t)(void *priv, const char *id, int index,
>