[PATCH 0/2] qcom: remove memcpy()ing from cmd-db driver

[PATCH 0/2] qcom: remove memcpy()ing from cmd-db driver

[Stephen Boyd]

Some changes to the cmd-db code to not do any more copying
of memory. Instead, we'll just hand out pointers to things
inside cmd-db. Merging the second patch will cause problems
for any in-flight users of the cmd-db APIs that are modified
and/or removed. Probably that patch can wait until later, or 
I can provide the fixes for any patches in-flight that get
wrecked when it's applied.

Cc: Mahesh Sivasubramanian <msivasub@codeaurora.org>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Evan Green <evgreen@chromium.org>

Stephen Boyd (2):
  soc: qcom: cmd-db: Remove memcpy()ing from cmd_db_get_header()
  soc: qcom: cmd-db: Stop memcpy()ing in cmd_db_read_aux_data()

 drivers/soc/qcom/cmd-db.c | 93 ++++++++++++---------------------------
 include/soc/qcom/cmd-db.h | 12 ++---
 2 files changed, 32 insertions(+), 73 deletions(-)

-- 
Sent by a computer through tubes

[PATCH 1/2] soc: qcom: cmd-db: Remove memcpy()ing from cmd_db_get_header()

[Stephen Boyd]

The cmd_db_get_header() function is a static local function that doesn't
need to copy anything from one place to another. Instead, it can just
point into the region by returning pointers to what we're looking for.
If we do that, we should mark what we're returning as const so that code
can't modify cmd-db without an obvious cast.

Cc: Mahesh Sivasubramanian <msivasub@codeaurora.org>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Evan Green <evgreen@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 drivers/soc/qcom/cmd-db.c | 60 +++++++++++++++++----------------------
 1 file changed, 26 insertions(+), 34 deletions(-)

diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c
index a6f646295f06..5c9cc6824891 100644
--- a/drivers/soc/qcom/cmd-db.c
+++ b/drivers/soc/qcom/cmd-db.c
@@ -101,8 +101,7 @@ static bool cmd_db_magic_matches(const struct cmd_db_header *header)
 
 static struct cmd_db_header *cmd_db_header;
 
-
-static inline void *rsc_to_entry_header(struct rsc_hdr *hdr)
+static inline const void *rsc_to_entry_header(const struct rsc_hdr *hdr)
 {
 	u16 offset = le16_to_cpu(hdr->header_offset);
 
@@ -110,7 +109,7 @@ static inline void *rsc_to_entry_header(struct rsc_hdr *hdr)
 }
 
 static inline void *
-rsc_offset(struct rsc_hdr *hdr, struct entry_header *ent)
+rsc_offset(const struct rsc_hdr *hdr, const struct entry_header *ent)
 {
 	u16 offset = le16_to_cpu(hdr->data_offset);
 	u16 loffset = le16_to_cpu(ent->offset);
@@ -134,11 +133,11 @@ int cmd_db_ready(void)
 }
 EXPORT_SYMBOL(cmd_db_ready);
 
-static int cmd_db_get_header(const char *id, struct entry_header *eh,
-			     struct rsc_hdr *rh)
+static int cmd_db_get_header(const char *id, const struct entry_header **eh,
+			     const struct rsc_hdr **rh)
 {
-	struct rsc_hdr *rsc_hdr;
-	struct entry_header *ent;
+	const struct rsc_hdr *rsc_hdr;
+	const struct entry_header *ent;
 	int ret, i, j;
 	u8 query[8];
 
@@ -146,9 +145,6 @@ static int cmd_db_get_header(const char *id, struct entry_header *eh,
 	if (ret)
 		return ret;
 
-	if (!eh || !rh)
-		return -EINVAL;
-
 	/* Pad out query string to same length as in DB */
 	strncpy(query, id, sizeof(query));
 
@@ -159,14 +155,13 @@ static int cmd_db_get_header(const char *id, struct entry_header *eh,
 
 		ent = rsc_to_entry_header(rsc_hdr);
 		for (j = 0; j < le16_to_cpu(rsc_hdr->cnt); j++, ent++) {
-			if (memcmp(ent->id, query, sizeof(ent->id)) == 0)
-				break;
-		}
-
-		if (j < le16_to_cpu(rsc_hdr->cnt)) {
-			memcpy(eh, ent, sizeof(*ent));
-			memcpy(rh, rsc_hdr, sizeof(*rh));
-			return 0;
+			if (memcmp(ent->id, query, sizeof(ent->id)) == 0) {
+				if (eh)
+					*eh = ent;
+				if (rh)
+					*rh = rsc_hdr;
+				return 0;
+			}
 		}
 	}
 
@@ -186,12 +181,11 @@ static int cmd_db_get_header(const char *id, struct entry_header *eh,
 u32 cmd_db_read_addr(const char *id)
 {
 	int ret;
-	struct entry_header ent;
-	struct rsc_hdr rsc_hdr;
+	const struct entry_header *ent;
 
-	ret = cmd_db_get_header(id, &ent, &rsc_hdr);
+	ret = cmd_db_get_header(id, &ent, NULL);
 
-	return ret < 0 ? 0 : le32_to_cpu(ent.addr);
+	return ret < 0 ? 0 : le32_to_cpu(ent->addr);
 }
 EXPORT_SYMBOL(cmd_db_read_addr);
 
@@ -207,8 +201,8 @@ EXPORT_SYMBOL(cmd_db_read_addr);
 int cmd_db_read_aux_data(const char *id, u8 *data, size_t len)
 {
 	int ret;
-	struct entry_header ent;
-	struct rsc_hdr rsc_hdr;
+	const struct entry_header *ent;
+	const struct rsc_hdr *rsc_hdr;
 	u16 ent_len;
 
 	if (!data)
@@ -218,12 +212,12 @@ int cmd_db_read_aux_data(const char *id, u8 *data, size_t len)
 	if (ret)
 		return ret;
 
-	ent_len = le16_to_cpu(ent.len);
+	ent_len = le16_to_cpu(ent->len);
 	if (len < ent_len)
 		return -EINVAL;
 
 	len = min_t(u16, ent_len, len);
-	memcpy(data, rsc_offset(&rsc_hdr, &ent), len);
+	memcpy(data, rsc_offset(rsc_hdr, ent), len);
 
 	return len;
 }
@@ -239,12 +233,11 @@ EXPORT_SYMBOL(cmd_db_read_aux_data);
 size_t cmd_db_read_aux_data_len(const char *id)
 {
 	int ret;
-	struct entry_header ent;
-	struct rsc_hdr rsc_hdr;
+	const struct entry_header *ent;
 
-	ret = cmd_db_get_header(id, &ent, &rsc_hdr);
+	ret = cmd_db_get_header(id, &ent, NULL);
 
-	return ret < 0 ? 0 : le16_to_cpu(ent.len);
+	return ret < 0 ? 0 : le16_to_cpu(ent->len);
 }
 EXPORT_SYMBOL(cmd_db_read_aux_data_len);
 
@@ -258,15 +251,14 @@ EXPORT_SYMBOL(cmd_db_read_aux_data_len);
 enum cmd_db_hw_type cmd_db_read_slave_id(const char *id)
 {
 	int ret;
-	struct entry_header ent;
-	struct rsc_hdr rsc_hdr;
+	const struct entry_header *ent;
 	u32 addr;
 
-	ret = cmd_db_get_header(id, &ent, &rsc_hdr);
+	ret = cmd_db_get_header(id, &ent, NULL);
 	if (ret < 0)
 		return CMD_DB_HW_INVALID;
 
-	addr = le32_to_cpu(ent.addr);
+	addr = le32_to_cpu(ent->addr);
 	return (addr >> SLAVE_ID_SHIFT) & SLAVE_ID_MASK;
 }
 EXPORT_SYMBOL(cmd_db_read_slave_id);
-- 
Sent by a computer through tubes

[PATCH 2/2] soc: qcom: cmd-db: Stop memcpy()ing in cmd_db_read_aux_data()

[Stephen Boyd]

Let's change the function signature to return the pointer to memory or
an error pointer on failure, and take an argument that lets us return
the size of the aux data read. This way we can remove the
cmd_db_read_aux_data_len() API entirely and also get rid of the memcpy
operation from cmd_db to the caller.

Cc: Mahesh Sivasubramanian <msivasub@codeaurora.org>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Evan Green <evgreen@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 drivers/soc/qcom/cmd-db.c | 43 ++++++++-------------------------------
 include/soc/qcom/cmd-db.h | 12 +++--------
 2 files changed, 11 insertions(+), 44 deletions(-)

diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c
index 5c9cc6824891..c701b3b010f1 100644
--- a/drivers/soc/qcom/cmd-db.c
+++ b/drivers/soc/qcom/cmd-db.c
@@ -192,55 +192,28 @@ EXPORT_SYMBOL(cmd_db_read_addr);
 /**
  * cmd_db_read_aux_data() - Query command db for aux data.
  *
- *  @id: Resource to retrieve AUX Data on.
- *  @data: Data buffer to copy returned aux data to. Returns size on NULL
- *  @len: Caller provides size of data buffer passed in.
+ *  @id: Resource to retrieve AUX Data on
+ *  @len: size of data buffer returned
  *
- *  Return: size of data on success, errno otherwise
+ *  Return: pointer to data on success, error pointer otherwise
  */
-int cmd_db_read_aux_data(const char *id, u8 *data, size_t len)
+const void *cmd_db_read_aux_data(const char *id, size_t *len)
 {
 	int ret;
 	const struct entry_header *ent;
 	const struct rsc_hdr *rsc_hdr;
-	u16 ent_len;
-
-	if (!data)
-		return -EINVAL;
 
 	ret = cmd_db_get_header(id, &ent, &rsc_hdr);
 	if (ret)
-		return ret;
-
-	ent_len = le16_to_cpu(ent->len);
-	if (len < ent_len)
-		return -EINVAL;
+		return ERR_PTR(ret);
 
-	len = min_t(u16, ent_len, len);
-	memcpy(data, rsc_offset(rsc_hdr, ent), len);
+	if (len)
+		*len = le16_to_cpu(ent->len);
 
-	return len;
+	return rsc_offset(rsc_hdr, ent);
 }
 EXPORT_SYMBOL(cmd_db_read_aux_data);
 
-/**
- * cmd_db_read_aux_data_len - Get the length of the auxiliary data stored in DB.
- *
- * @id: Resource to retrieve AUX Data.
- *
- * Return: size on success, 0 on error
- */
-size_t cmd_db_read_aux_data_len(const char *id)
-{
-	int ret;
-	const struct entry_header *ent;
-
-	ret = cmd_db_get_header(id, &ent, NULL);
-
-	return ret < 0 ? 0 : le16_to_cpu(ent->len);
-}
-EXPORT_SYMBOL(cmd_db_read_aux_data_len);
-
 /**
  * cmd_db_read_slave_id - Get the slave ID for a given resource address
  *
diff --git a/include/soc/qcom/cmd-db.h b/include/soc/qcom/cmd-db.h
index 578180cbc134..af9722223925 100644
--- a/include/soc/qcom/cmd-db.h
+++ b/include/soc/qcom/cmd-db.h
@@ -18,9 +18,7 @@ enum cmd_db_hw_type {
 #if IS_ENABLED(CONFIG_QCOM_COMMAND_DB)
 u32 cmd_db_read_addr(const char *resource_id);
 
-int cmd_db_read_aux_data(const char *resource_id, u8 *data, size_t len);
-
-size_t cmd_db_read_aux_data_len(const char *resource_id);
+const void *cmd_db_read_aux_data(const char *resource_id, size_t *len);
 
 enum cmd_db_hw_type cmd_db_read_slave_id(const char *resource_id);
 
@@ -29,12 +27,8 @@ int cmd_db_ready(void);
 static inline u32 cmd_db_read_addr(const char *resource_id)
 { return 0; }
 
-static inline int cmd_db_read_aux_data(const char *resource_id, u8 *data,
-				       size_t len)
-{ return -ENODEV; }
-
-static inline size_t cmd_db_read_aux_data_len(const char *resource_id)
-{ return -ENODEV; }
+static inline const void *cmd_db_read_aux_data(const char *resource_id, size_t *len)
+{ return ERR_PTR(-ENODEV); }
 
 static inline enum cmd_db_hw_type cmd_db_read_slave_id(const char *resource_id)
 { return -ENODEV; }
-- 
Sent by a computer through tubes

Re: [PATCH 0/2] qcom: remove memcpy()ing from cmd-db driver

[Andy Gross]

On Tue, Jul 17, 2018 at 01:29:45PM -0700, Stephen Boyd wrote:
> Some changes to the cmd-db code to not do any more copying
> of memory. Instead, we'll just hand out pointers to things
> inside cmd-db. Merging the second patch will cause problems
> for any in-flight users of the cmd-db APIs that are modified
> and/or removed. Probably that patch can wait until later, or 
> I can provide the fixes for any patches in-flight that get
> wrecked when it's applied.

The Adreno folks picked up the cmd-db APIs and ran with them.  I'll
need an additional patch to fix that breakage.  You can see this in
4.19-rc1.

Thanks,

Andy

Re: [PATCH 0/2] qcom: remove memcpy()ing from cmd-db driver

[Stephen Boyd]

Quoting Andy Gross (2018-09-13 14:30:36)
> On Tue, Jul 17, 2018 at 01:29:45PM -0700, Stephen Boyd wrote:
> > Some changes to the cmd-db code to not do any more copying
> > of memory. Instead, we'll just hand out pointers to things
> > inside cmd-db. Merging the second patch will cause problems
> > for any in-flight users of the cmd-db APIs that are modified
> > and/or removed. Probably that patch can wait until later, or 
> > I can provide the fixes for any patches in-flight that get
> > wrecked when it's applied.
> 
> The Adreno folks picked up the cmd-db APIs and ran with them.  I'll
> need an additional patch to fix that breakage.  You can see this in
> 4.19-rc1.
> 

I'll resend. I already had fixed it a few weeks ago.