[PATCH v3 0/2] mtd: spi-nor: support dumping sfdp tables

[PATCH v3 0/2] mtd: spi-nor: support dumping sfdp tables

[Michael Walle]

Add the possibility to dump the SFDP data of a flash device.

More and more flash devices share the same flash ID and we need per device
fixups. Usually, these fixups differentiate flashes by looking at
differences in the SFDP data. Determining the difference is only possible
if we have the SFDP data for all the flashes which share a flash ID. This
will lay the foundation to dump the whole SFDP data of a flash device.

This is even more important, because some datasheets doesn't even contain
the SFDP data. Fixups for these kind of flashes are nearly impossible to
do.

I envision having a database of all the SFDP data for the flashes we
support and make it a requirement to submit it when a new flash is added.
This might or might not have legal implications. Thus I'd start with having
that database private to the SPI NOR maintainers.

Changes since v2:
 - use .dev_groups of the driver to attach the attributes
 - add manufacturer attribue
 - rename attribute name to partname
 - add ABI documentation

Changes since v1:
 - use sysfs_emit()
 - add comment about the allocation of the sfdp dwords
 - free SFDP memory in the error path
 - use BIN_ATTR_RO(sfdp, 0)
 - use spi_nor_read_sfdp()

Changes since RFC:
 - Don't read SFDP data after probe. The flash might already be switched to
   8D-8D-8D mode. Instead, cache the SFDP data
 - add two sysfs files: jedec-id and name
 - change the file mode of the sfdp file from 0400 to 0444. There is no
   hardware access anymore.

Michael Walle (2):
  mtd: spi-nor: sfdp: save a copy of the SFDP data
  mtd: spi-nor: add initial sysfs support

 .../ABI/testing/sysfs-bus-spi-devices-spi-nor | 31 +++++++
 drivers/mtd/spi-nor/Makefile                  |  2 +-
 drivers/mtd/spi-nor/core.c                    |  1 +
 drivers/mtd/spi-nor/core.h                    | 12 +++
 drivers/mtd/spi-nor/sfdp.c                    | 58 ++++++++++++
 drivers/mtd/spi-nor/sysfs.c                   | 92 +++++++++++++++++++
 include/linux/mtd/spi-nor.h                   |  2 +
 7 files changed, 197 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
 create mode 100644 drivers/mtd/spi-nor/sysfs.c

-- 
2.20.1

[PATCH v3 1/2] mtd: spi-nor: sfdp: save a copy of the SFDP data

[Michael Walle]

Due to possible mode switching to 8D-8D-8D, it might not be possible to
read the SFDP after the initial probe. To be able to dump the SFDP via
sysfs afterwards, make a complete copy of it.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Tested-by: Heiko Thiery <heiko.thiery@gmail.com>
---
 drivers/mtd/spi-nor/core.h  | 10 +++++++
 drivers/mtd/spi-nor/sfdp.c  | 58 +++++++++++++++++++++++++++++++++++++
 include/linux/mtd/spi-nor.h |  2 ++
 3 files changed, 70 insertions(+)

diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index b410e4eec2fb..92ee2f6551b3 100644
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -460,6 +460,16 @@ struct spi_nor_manufacturer {
 	const struct spi_nor_fixups *fixups;
 };
 
+/**
+ * struct sfdp - SFDP data
+ * @num_dwords: number of entries in the dwords array
+ * @dwords: array of double words of the SFDP data
+ */
+struct sfdp {
+	size_t	num_dwords;
+	u32	*dwords;
+};
+
 /* Manufacturer drivers. */
 extern const struct spi_nor_manufacturer spi_nor_atmel;
 extern const struct spi_nor_manufacturer spi_nor_catalyst;
diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
index 23c28e91f698..c500c2118a5d 100644
--- a/drivers/mtd/spi-nor/sfdp.c
+++ b/drivers/mtd/spi-nor/sfdp.c
@@ -16,6 +16,7 @@
 	(((p)->parameter_table_pointer[2] << 16) | \
 	 ((p)->parameter_table_pointer[1] <<  8) | \
 	 ((p)->parameter_table_pointer[0] <<  0))
+#define SFDP_PARAM_HEADER_PARAM_LEN(p) ((p)->length * 4)
 
 #define SFDP_BFPT_ID		0xff00	/* Basic Flash Parameter Table */
 #define SFDP_SECTOR_MAP_ID	0xff81	/* Sector Map Table */
@@ -1245,6 +1246,8 @@ int spi_nor_parse_sfdp(struct spi_nor *nor)
 	struct sfdp_parameter_header *param_headers = NULL;
 	struct sfdp_header header;
 	struct device *dev = nor->dev;
+	struct sfdp *sfdp;
+	size_t sfdp_size;
 	size_t psize;
 	int i, err;
 
@@ -1267,6 +1270,9 @@ int spi_nor_parse_sfdp(struct spi_nor *nor)
 	    bfpt_header->major != SFDP_JESD216_MAJOR)
 		return -EINVAL;
 
+	sfdp_size = SFDP_PARAM_HEADER_PTP(bfpt_header) +
+		    SFDP_PARAM_HEADER_PARAM_LEN(bfpt_header);
+
 	/*
 	 * Allocate memory then read all parameter headers with a single
 	 * Read SFDP command. These parameter headers will actually be parsed
@@ -1293,6 +1299,58 @@ int spi_nor_parse_sfdp(struct spi_nor *nor)
 		}
 	}
 
+	/*
+	 * Cache the complete SFDP data. It is not (easily) possible to fetch
+	 * SFDP after probe time and we need it for the sysfs access.
+	 */
+	for (i = 0; i < header.nph; i++) {
+		param_header = &param_headers[i];
+		sfdp_size = max_t(size_t, sfdp_size,
+				  SFDP_PARAM_HEADER_PTP(param_header) +
+				  SFDP_PARAM_HEADER_PARAM_LEN(param_header));
+	}
+
+	/*
+	 * Limit the total size to a reasonable value to avoid allocating too
+	 * much memory just of because the flash returned some insane values.
+	 */
+	if (sfdp_size > PAGE_SIZE) {
+		dev_dbg(dev, "SFDP data (%zu) too big, truncating\n",
+			sfdp_size);
+		sfdp_size = PAGE_SIZE;
+	}
+
+	sfdp = devm_kzalloc(dev, sizeof(*sfdp), GFP_KERNEL);
+	if (!sfdp) {
+		err = -ENOMEM;
+		goto exit;
+	}
+
+	/*
+	 * The SFDP is organized in chunks of DWORDs. Thus, in theory, the
+	 * sfdp_size should be a multiple of DWORDs. But in case a flash
+	 * is not spec compliant, make sure that we have enough space to store
+	 * the complete SFDP data.
+	 */
+	sfdp->num_dwords = DIV_ROUND_UP(sfdp_size, sizeof(*sfdp->dwords));
+	sfdp->dwords = devm_kcalloc(dev, sfdp->num_dwords,
+				    sizeof(*sfdp->dwords), GFP_KERNEL);
+	if (!sfdp->dwords) {
+		err = -ENOMEM;
+		devm_kfree(dev, sfdp);
+		goto exit;
+	}
+
+	err = spi_nor_read_sfdp(nor, 0, sfdp_size, sfdp->dwords);
+	if (err < 0) {
+		dev_dbg(dev, "failed to read SFDP data\n");
+		devm_kfree(dev, sfdp->dwords);
+		devm_kfree(dev, sfdp);
+		goto exit;
+	}
+
+	nor->sfdp = sfdp;
+
 	/*
 	 * Check other parameter headers to get the latest revision of
 	 * the basic flash parameter table.
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index 98ed91b529ea..f67457748ed8 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -383,6 +383,7 @@ struct spi_nor_flash_parameter;
  * @read_proto:		the SPI protocol for read operations
  * @write_proto:	the SPI protocol for write operations
  * @reg_proto:		the SPI protocol for read_reg/write_reg/erase operations
+ * @sfdp:		the SFDP data of the flash
  * @controller_ops:	SPI NOR controller driver specific operations.
  * @params:		[FLASH-SPECIFIC] SPI NOR flash parameters and settings.
  *                      The structure includes legacy flash parameters and
@@ -412,6 +413,7 @@ struct spi_nor {
 	bool			sst_write_second;
 	u32			flags;
 	enum spi_nor_cmd_ext	cmd_ext_type;
+	struct sfdp		*sfdp;
 
 	const struct spi_nor_controller_ops *controller_ops;
 
-- 
2.20.1

[PATCH v3 2/2] mtd: spi-nor: add initial sysfs support

[Michael Walle]

Add support to show the manufacturer, the partname and JEDEC identifier
as well as to dump the SFDP table. Not all flashes list their SFDP table
contents in their datasheet. So having that is useful. It might also be
helpful in bug reports from users.

Signed-off-by: Michael Walle <michael@walle.cc>
---
Pratyush, Heiko, I've dropped your Acked and Tested-by because there
were some changes.

 .../ABI/testing/sysfs-bus-spi-devices-spi-nor | 31 +++++++
 drivers/mtd/spi-nor/Makefile                  |  2 +-
 drivers/mtd/spi-nor/core.c                    |  1 +
 drivers/mtd/spi-nor/core.h                    |  2 +
 drivers/mtd/spi-nor/sysfs.c                   | 92 +++++++++++++++++++
 5 files changed, 127 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
 create mode 100644 drivers/mtd/spi-nor/sysfs.c

diff --git a/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor b/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
new file mode 100644
index 000000000000..4c88307759e2
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
@@ -0,0 +1,31 @@
+What:		/sys/bus/spi/devices/.../jedec_id
+Date:		April 2021
+KernelVersion:	5.14
+Contact:	linux-mtd@lists.infradead.org
+Description:	(RO) The JEDEC ID of the SPI NOR flash as reported by the
+		flash device.
+
+
+What:		/sys/bus/spi/devices/.../manufacturer
+Date:		April 2021
+KernelVersion:	5.14
+Contact:	linux-mtd@lists.infradead.org
+Description:	(RO) Manufacturer of the SPI NOR flash.
+
+
+What:		/sys/bus/spi/devices/.../partname
+Date:		April 2021
+KernelVersion:	5.14
+Contact:	linux-mtd@lists.infradead.org
+Description:	(RO) Part name of the SPI NOR flash.
+
+
+What:		/sys/bus/spi/devices/.../sfdp
+Date:		April 2021
+KernelVersion:	5.14
+Contact:	linux-mtd@lists.infradead.org
+Description:	(RO) This attribute is only present if the SPI NOR flash
+		device supports the "Read SFDP" command (5Ah).
+
+		If present, it contains the complete SFDP (serial flash
+		discoverable parameters) binary data of the flash.
diff --git a/drivers/mtd/spi-nor/Makefile b/drivers/mtd/spi-nor/Makefile
index 136f245c91dc..6b904e439372 100644
--- a/drivers/mtd/spi-nor/Makefile
+++ b/drivers/mtd/spi-nor/Makefile
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 
-spi-nor-objs			:= core.o sfdp.o swp.o otp.o
+spi-nor-objs			:= core.o sfdp.o swp.o otp.o sysfs.o
 spi-nor-objs			+= atmel.o
 spi-nor-objs			+= catalyst.o
 spi-nor-objs			+= eon.o
diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 20c7ee604731..57d8a4dae5fd 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -3349,6 +3349,7 @@ static struct spi_mem_driver spi_nor_driver = {
 		.driver = {
 			.name = "spi-nor",
 			.of_match_table = spi_nor_of_table,
+			.dev_groups = spi_nor_sysfs_groups,
 		},
 		.id_table = spi_nor_dev_ids,
 	},
diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index 92ee2f6551b3..b988e5e64b2d 100644
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -489,6 +489,8 @@ extern const struct spi_nor_manufacturer spi_nor_winbond;
 extern const struct spi_nor_manufacturer spi_nor_xilinx;
 extern const struct spi_nor_manufacturer spi_nor_xmc;
 
+extern const struct attribute_group *spi_nor_sysfs_groups[];
+
 void spi_nor_spimem_setup_op(const struct spi_nor *nor,
 			     struct spi_mem_op *op,
 			     const enum spi_nor_protocol proto);
diff --git a/drivers/mtd/spi-nor/sysfs.c b/drivers/mtd/spi-nor/sysfs.c
new file mode 100644
index 000000000000..8f1aad4061cd
--- /dev/null
+++ b/drivers/mtd/spi-nor/sysfs.c
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/mtd/spi-nor.h>
+#include <linux/spi/spi.h>
+#include <linux/spi/spi-mem.h>
+#include <linux/sysfs.h>
+
+#include "core.h"
+
+static ssize_t manufacturer_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	struct spi_mem *spimem = spi_get_drvdata(spi);
+	struct spi_nor *nor = spi_mem_get_drvdata(spimem);
+
+	return sysfs_emit(buf, "%s\n", nor->manufacturer->name);
+}
+static DEVICE_ATTR_RO(manufacturer);
+
+static ssize_t partname_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	struct spi_mem *spimem = spi_get_drvdata(spi);
+	struct spi_nor *nor = spi_mem_get_drvdata(spimem);
+
+	return sysfs_emit(buf, "%s\n", nor->info->name);
+}
+static DEVICE_ATTR_RO(partname);
+
+static ssize_t jedec_id_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	struct spi_mem *spimem = spi_get_drvdata(spi);
+	struct spi_nor *nor = spi_mem_get_drvdata(spimem);
+
+	return sysfs_emit(buf, "%*phN\n", nor->info->id_len, nor->info->id);
+}
+static DEVICE_ATTR_RO(jedec_id);
+
+static struct attribute *spi_nor_sysfs_entries[] = {
+	&dev_attr_manufacturer.attr,
+	&dev_attr_partname.attr,
+	&dev_attr_jedec_id.attr,
+	NULL
+};
+
+static ssize_t sfdp_read(struct file *filp, struct kobject *kobj,
+			 struct bin_attribute *bin_attr, char *buf,
+			 loff_t off, size_t count)
+{
+	struct spi_device *spi = to_spi_device(kobj_to_dev(kobj));
+	struct spi_mem *spimem = spi_get_drvdata(spi);
+	struct spi_nor *nor = spi_mem_get_drvdata(spimem);
+	struct sfdp *sfdp = nor->sfdp;
+	size_t sfdp_size = sfdp->num_dwords * sizeof(*sfdp->dwords);
+
+	return memory_read_from_buffer(buf, count, &off, nor->sfdp->dwords,
+				       sfdp_size);
+}
+static BIN_ATTR_RO(sfdp, 0);
+
+static struct bin_attribute *spi_nor_sysfs_bin_entries[] = {
+	&bin_attr_sfdp,
+	NULL
+};
+
+static umode_t spi_nor_sysfs_is_bin_visible(struct kobject *kobj,
+					    struct bin_attribute *attr, int n)
+{
+	struct spi_device *spi = to_spi_device(kobj_to_dev(kobj));
+	struct spi_mem *spimem = spi_get_drvdata(spi);
+	struct spi_nor *nor = spi_mem_get_drvdata(spimem);
+
+	if (attr == &bin_attr_sfdp && nor->sfdp)
+		return 0444;
+
+	return 0;
+}
+
+static const struct attribute_group spi_nor_sysfs_group = {
+	.is_bin_visible	= spi_nor_sysfs_is_bin_visible,
+	.attrs		= spi_nor_sysfs_entries,
+	.bin_attrs	= spi_nor_sysfs_bin_entries,
+};
+
+const struct attribute_group *spi_nor_sysfs_groups[] = {
+	&spi_nor_sysfs_group,
+	NULL
+};
-- 
2.20.1

Re: [PATCH v3 2/2] mtd: spi-nor: add initial sysfs support

[Alexander Williams]

Hi Michael,

On Thu, Apr 29, 2021 at 8:57 AM Michael Walle <michael@walle.cc> wrote:
>
> Add support to show the manufacturer, the partname and JEDEC identifier
> as well as to dump the SFDP table. Not all flashes list their SFDP table
> contents in their datasheet. So having that is useful. It might also be
> helpful in bug reports from users.
>
> Signed-off-by: Michael Walle <michael@walle.cc>
> ---
> Pratyush, Heiko, I've dropped your Acked and Tested-by because there
> were some changes.
>
>  .../ABI/testing/sysfs-bus-spi-devices-spi-nor | 31 +++++++
>  drivers/mtd/spi-nor/Makefile                  |  2 +-
>  drivers/mtd/spi-nor/core.c                    |  1 +
>  drivers/mtd/spi-nor/core.h                    |  2 +
>  drivers/mtd/spi-nor/sysfs.c                   | 92 +++++++++++++++++++
>  5 files changed, 127 insertions(+), 1 deletion(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
>  create mode 100644 drivers/mtd/spi-nor/sysfs.c
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor b/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
> new file mode 100644
> index 000000000000..4c88307759e2
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
> @@ -0,0 +1,31 @@
> +What:          /sys/bus/spi/devices/.../jedec_id
> +Date:          April 2021
> +KernelVersion: 5.14
> +Contact:       linux-mtd@lists.infradead.org
> +Description:   (RO) The JEDEC ID of the SPI NOR flash as reported by the
> +               flash device.
> +
> +
> +What:          /sys/bus/spi/devices/.../manufacturer
> +Date:          April 2021
> +KernelVersion: 5.14
> +Contact:       linux-mtd@lists.infradead.org
> +Description:   (RO) Manufacturer of the SPI NOR flash.
> +
> +
> +What:          /sys/bus/spi/devices/.../partname
> +Date:          April 2021
> +KernelVersion: 5.14
> +Contact:       linux-mtd@lists.infradead.org
> +Description:   (RO) Part name of the SPI NOR flash.
> +
> +
> +What:          /sys/bus/spi/devices/.../sfdp
> +Date:          April 2021
> +KernelVersion: 5.14
> +Contact:       linux-mtd@lists.infradead.org
> +Description:   (RO) This attribute is only present if the SPI NOR flash
> +               device supports the "Read SFDP" command (5Ah).
> +
> +               If present, it contains the complete SFDP (serial flash
> +               discoverable parameters) binary data of the flash.
> diff --git a/drivers/mtd/spi-nor/Makefile b/drivers/mtd/spi-nor/Makefile
> index 136f245c91dc..6b904e439372 100644
> --- a/drivers/mtd/spi-nor/Makefile
> +++ b/drivers/mtd/spi-nor/Makefile
> @@ -1,6 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0
>
> -spi-nor-objs                   := core.o sfdp.o swp.o otp.o
> +spi-nor-objs                   := core.o sfdp.o swp.o otp.o sysfs.o
>  spi-nor-objs                   += atmel.o
>  spi-nor-objs                   += catalyst.o
>  spi-nor-objs                   += eon.o
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index 20c7ee604731..57d8a4dae5fd 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -3349,6 +3349,7 @@ static struct spi_mem_driver spi_nor_driver = {
>                 .driver = {
>                         .name = "spi-nor",
>                         .of_match_table = spi_nor_of_table,
> +                       .dev_groups = spi_nor_sysfs_groups,

Putting these in the driver's dev_groups does create a divergence between
different spi-nor controllers. For all the controllers supported in
drivers/mtd/spi-nor/controllers/, would their drivers need to add the same sysfs
groups to get the same support?

- Alex

Re: [PATCH v3 2/2] mtd: spi-nor: add initial sysfs support

[Michael Walle]

Hi Alex,

Am 2021-04-29 18:23, schrieb Alexander Williams:
> On Thu, Apr 29, 2021 at 8:57 AM Michael Walle <michael@walle.cc> wrote:
>> 
>> Add support to show the manufacturer, the partname and JEDEC 
>> identifier
>> as well as to dump the SFDP table. Not all flashes list their SFDP 
>> table
>> contents in their datasheet. So having that is useful. It might also 
>> be
>> helpful in bug reports from users.
>> 
>> Signed-off-by: Michael Walle <michael@walle.cc>
>> ---
>> Pratyush, Heiko, I've dropped your Acked and Tested-by because there
>> were some changes.
>> 
>>  .../ABI/testing/sysfs-bus-spi-devices-spi-nor | 31 +++++++
>>  drivers/mtd/spi-nor/Makefile                  |  2 +-
>>  drivers/mtd/spi-nor/core.c                    |  1 +
>>  drivers/mtd/spi-nor/core.h                    |  2 +
>>  drivers/mtd/spi-nor/sysfs.c                   | 92 
>> +++++++++++++++++++
>>  5 files changed, 127 insertions(+), 1 deletion(-)
>>  create mode 100644 
>> Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
>>  create mode 100644 drivers/mtd/spi-nor/sysfs.c
>> 
>> diff --git a/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor 
>> b/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
>> new file mode 100644
>> index 000000000000..4c88307759e2
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
>> @@ -0,0 +1,31 @@
>> +What:          /sys/bus/spi/devices/.../jedec_id
>> +Date:          April 2021
>> +KernelVersion: 5.14
>> +Contact:       linux-mtd@lists.infradead.org
>> +Description:   (RO) The JEDEC ID of the SPI NOR flash as reported by 
>> the
>> +               flash device.
>> +
>> +
>> +What:          /sys/bus/spi/devices/.../manufacturer
>> +Date:          April 2021
>> +KernelVersion: 5.14
>> +Contact:       linux-mtd@lists.infradead.org
>> +Description:   (RO) Manufacturer of the SPI NOR flash.
>> +
>> +
>> +What:          /sys/bus/spi/devices/.../partname
>> +Date:          April 2021
>> +KernelVersion: 5.14
>> +Contact:       linux-mtd@lists.infradead.org
>> +Description:   (RO) Part name of the SPI NOR flash.
>> +
>> +
>> +What:          /sys/bus/spi/devices/.../sfdp
>> +Date:          April 2021
>> +KernelVersion: 5.14
>> +Contact:       linux-mtd@lists.infradead.org
>> +Description:   (RO) This attribute is only present if the SPI NOR 
>> flash
>> +               device supports the "Read SFDP" command (5Ah).
>> +
>> +               If present, it contains the complete SFDP (serial 
>> flash
>> +               discoverable parameters) binary data of the flash.
>> diff --git a/drivers/mtd/spi-nor/Makefile 
>> b/drivers/mtd/spi-nor/Makefile
>> index 136f245c91dc..6b904e439372 100644
>> --- a/drivers/mtd/spi-nor/Makefile
>> +++ b/drivers/mtd/spi-nor/Makefile
>> @@ -1,6 +1,6 @@
>>  # SPDX-License-Identifier: GPL-2.0
>> 
>> -spi-nor-objs                   := core.o sfdp.o swp.o otp.o
>> +spi-nor-objs                   := core.o sfdp.o swp.o otp.o sysfs.o
>>  spi-nor-objs                   += atmel.o
>>  spi-nor-objs                   += catalyst.o
>>  spi-nor-objs                   += eon.o
>> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
>> index 20c7ee604731..57d8a4dae5fd 100644
>> --- a/drivers/mtd/spi-nor/core.c
>> +++ b/drivers/mtd/spi-nor/core.c
>> @@ -3349,6 +3349,7 @@ static struct spi_mem_driver spi_nor_driver = {
>>                 .driver = {
>>                         .name = "spi-nor",
>>                         .of_match_table = spi_nor_of_table,
>> +                       .dev_groups = spi_nor_sysfs_groups,
> 
> Putting these in the driver's dev_groups does create a divergence 
> between
> different spi-nor controllers. For all the controllers supported in
> drivers/mtd/spi-nor/controllers/, would their drivers need to add the 
> same sysfs
> groups to get the same support?

Well, one supports it and one does not, no? If support is added later,
we should keep an eye on it. Unfortunately, I don't have any hardware
to see if just adding the .dev_groups to another driver will just work.

-michael

Re: [PATCH v3 2/2] mtd: spi-nor: add initial sysfs support

[Alexander Williams]

On Thu, Apr 29, 2021 at 9:44 AM Michael Walle <michael@walle.cc> wrote:
>
> Hi Alex,
>
> Am 2021-04-29 18:23, schrieb Alexander Williams:
> > On Thu, Apr 29, 2021 at 8:57 AM Michael Walle <michael@walle.cc> wrote:
> >>
> >> Add support to show the manufacturer, the partname and JEDEC
> >> identifier
> >> as well as to dump the SFDP table. Not all flashes list their SFDP
> >> table
> >> contents in their datasheet. So having that is useful. It might also
> >> be
> >> helpful in bug reports from users.
> >>
> >> Signed-off-by: Michael Walle <michael@walle.cc>
> >> ---
> >> Pratyush, Heiko, I've dropped your Acked and Tested-by because there
> >> were some changes.
> >>
> >>  .../ABI/testing/sysfs-bus-spi-devices-spi-nor | 31 +++++++
> >>  drivers/mtd/spi-nor/Makefile                  |  2 +-
> >>  drivers/mtd/spi-nor/core.c                    |  1 +
> >>  drivers/mtd/spi-nor/core.h                    |  2 +
> >>  drivers/mtd/spi-nor/sysfs.c                   | 92
> >> +++++++++++++++++++
> >>  5 files changed, 127 insertions(+), 1 deletion(-)
> >>  create mode 100644
> >> Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
> >>  create mode 100644 drivers/mtd/spi-nor/sysfs.c
> >>
> >> diff --git a/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
> >> b/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
> >> new file mode 100644
> >> index 000000000000..4c88307759e2
> >> --- /dev/null
> >> +++ b/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
> >> @@ -0,0 +1,31 @@
> >> +What:          /sys/bus/spi/devices/.../jedec_id
> >> +Date:          April 2021
> >> +KernelVersion: 5.14
> >> +Contact:       linux-mtd@lists.infradead.org
> >> +Description:   (RO) The JEDEC ID of the SPI NOR flash as reported by
> >> the
> >> +               flash device.
> >> +
> >> +
> >> +What:          /sys/bus/spi/devices/.../manufacturer
> >> +Date:          April 2021
> >> +KernelVersion: 5.14
> >> +Contact:       linux-mtd@lists.infradead.org
> >> +Description:   (RO) Manufacturer of the SPI NOR flash.
> >> +
> >> +
> >> +What:          /sys/bus/spi/devices/.../partname
> >> +Date:          April 2021
> >> +KernelVersion: 5.14
> >> +Contact:       linux-mtd@lists.infradead.org
> >> +Description:   (RO) Part name of the SPI NOR flash.
> >> +
> >> +
> >> +What:          /sys/bus/spi/devices/.../sfdp
> >> +Date:          April 2021
> >> +KernelVersion: 5.14
> >> +Contact:       linux-mtd@lists.infradead.org
> >> +Description:   (RO) This attribute is only present if the SPI NOR
> >> flash
> >> +               device supports the "Read SFDP" command (5Ah).
> >> +
> >> +               If present, it contains the complete SFDP (serial
> >> flash
> >> +               discoverable parameters) binary data of the flash.
> >> diff --git a/drivers/mtd/spi-nor/Makefile
> >> b/drivers/mtd/spi-nor/Makefile
> >> index 136f245c91dc..6b904e439372 100644
> >> --- a/drivers/mtd/spi-nor/Makefile
> >> +++ b/drivers/mtd/spi-nor/Makefile
> >> @@ -1,6 +1,6 @@
> >>  # SPDX-License-Identifier: GPL-2.0
> >>
> >> -spi-nor-objs                   := core.o sfdp.o swp.o otp.o
> >> +spi-nor-objs                   := core.o sfdp.o swp.o otp.o sysfs.o
> >>  spi-nor-objs                   += atmel.o
> >>  spi-nor-objs                   += catalyst.o
> >>  spi-nor-objs                   += eon.o
> >> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> >> index 20c7ee604731..57d8a4dae5fd 100644
> >> --- a/drivers/mtd/spi-nor/core.c
> >> +++ b/drivers/mtd/spi-nor/core.c
> >> @@ -3349,6 +3349,7 @@ static struct spi_mem_driver spi_nor_driver = {
> >>                 .driver = {
> >>                         .name = "spi-nor",
> >>                         .of_match_table = spi_nor_of_table,
> >> +                       .dev_groups = spi_nor_sysfs_groups,
> >
> > Putting these in the driver's dev_groups does create a divergence
> > between
> > different spi-nor controllers. For all the controllers supported in
> > drivers/mtd/spi-nor/controllers/, would their drivers need to add the
> > same sysfs
> > groups to get the same support?
>
> Well, one supports it and one does not, no? If support is added later,
> we should keep an eye on it. Unfortunately, I don't have any hardware
> to see if just adding the .dev_groups to another driver will just work.

Right, I didn't mean to indicate opposition. Since mtd/spi-nor has certainly
got its set of quirky controllers and drivers (e.g. intel-spi does not support
reading the sfdp in its driver, currently), it might make sense to make these
attributes dependent on the driver. This mechanism also makes the attributes
available at KOBJ_BIND time, so spi_nor_scan() will have run, getting rid of
a pesky race condition with user space.

This comment was just to point out the implications and make sure you and
maintainers are okay with that approach.

- Alex

Re: [PATCH v3 2/2] mtd: spi-nor: add initial sysfs support

[Alexander Williams]

On Thu, Apr 29, 2021 at 8:57 AM Michael Walle <michael@walle.cc> wrote:
>
> Add support to show the manufacturer, the partname and JEDEC identifier
> as well as to dump the SFDP table. Not all flashes list their SFDP table
> contents in their datasheet. So having that is useful. It might also be
> helpful in bug reports from users.
>
> Signed-off-by: Michael Walle <michael@walle.cc>
> ---
> Pratyush, Heiko, I've dropped your Acked and Tested-by because there
> were some changes.
>
>  .../ABI/testing/sysfs-bus-spi-devices-spi-nor | 31 +++++++
>  drivers/mtd/spi-nor/Makefile                  |  2 +-
>  drivers/mtd/spi-nor/core.c                    |  1 +
>  drivers/mtd/spi-nor/core.h                    |  2 +
>  drivers/mtd/spi-nor/sysfs.c                   | 92 +++++++++++++++++++
>  5 files changed, 127 insertions(+), 1 deletion(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
>  create mode 100644 drivers/mtd/spi-nor/sysfs.c
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor b/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
> new file mode 100644
> index 000000000000..4c88307759e2
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
> @@ -0,0 +1,31 @@
> +What:          /sys/bus/spi/devices/.../jedec_id

Since mtd/spi-nor doesn't own this device (belongs to the spi subsystem), should
we put its attributes under a named subdirectory? Perhaps something like
/sys/bus/spi/devices/.../spi_nor/jedec_id ?

I'm just thinking about avoiding any potential for namespace clashes.
- Alex

Re: [PATCH v3 2/2] mtd: spi-nor: add initial sysfs support

[Michael Walle]

Am 2021-04-29 23:34, schrieb Alexander Williams:
> On Thu, Apr 29, 2021 at 8:57 AM Michael Walle <michael@walle.cc> wrote:
>> 
>> Add support to show the manufacturer, the partname and JEDEC 
>> identifier
>> as well as to dump the SFDP table. Not all flashes list their SFDP 
>> table
>> contents in their datasheet. So having that is useful. It might also 
>> be
>> helpful in bug reports from users.
>> 
>> Signed-off-by: Michael Walle <michael@walle.cc>
>> ---
>> Pratyush, Heiko, I've dropped your Acked and Tested-by because there
>> were some changes.
>> 
>>  .../ABI/testing/sysfs-bus-spi-devices-spi-nor | 31 +++++++
>>  drivers/mtd/spi-nor/Makefile                  |  2 +-
>>  drivers/mtd/spi-nor/core.c                    |  1 +
>>  drivers/mtd/spi-nor/core.h                    |  2 +
>>  drivers/mtd/spi-nor/sysfs.c                   | 92 
>> +++++++++++++++++++
>>  5 files changed, 127 insertions(+), 1 deletion(-)
>>  create mode 100644 
>> Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
>>  create mode 100644 drivers/mtd/spi-nor/sysfs.c
>> 
>> diff --git a/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor 
>> b/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
>> new file mode 100644
>> index 000000000000..4c88307759e2
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor
>> @@ -0,0 +1,31 @@
>> +What:          /sys/bus/spi/devices/.../jedec_id
> 
> Since mtd/spi-nor doesn't own this device (belongs to the spi 
> subsystem), should
> we put its attributes under a named subdirectory? Perhaps something 
> like
> /sys/bus/spi/devices/.../spi_nor/jedec_id ?
> 
> I'm just thinking about avoiding any potential for namespace clashes.

Good idea! Will change that in the next version.

-michael