Date:   Mon, 23 Apr 2018 11:22:30 -0600
From:   Lina Iyer <ilina@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Andy Gross <andy.gross@...aro.org>, linux-arm-msm@...r.kernel.org,
        linux-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mahesh Sivasubramanian <msivasub@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Evan Green <evgreen@...omium.org>
Subject: Re: [PATCH v3] soc: qcom: cmd-db: Make endian-agnostic

On Mon, Apr 23 2018 at 10:21 -0600, Stephen Boyd wrote:
>This driver deals with memory that is stored in little-endian format.
>Update the structures with the proper little-endian types and then
>do the proper conversions when reading the fields. Note that we compare
>the ids with a memcmp() because we already pad out the string 'id' field
>to exactly 8 bytes with the strncpy() onto the stack.
>
>Cc: Mahesh Sivasubramanian <msivasub@...eaurora.org>
>Cc: Lina Iyer <ilina@...eaurora.org>
>Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
>Cc: Evan Green <evgreen@...omium.org>
>Signed-off-by: Stephen Boyd <swboyd@...omium.org>
>---
>
Tested-by: Lina Iyer <ilina@...eaurora.org>

>Changes from v2:
> * Fixed rsc_offset conversion to use data_offset instead of header_offset
>   for finding first offset
> * Tested and confirmed slave ids and aux data for ARC regulators look
>   the same as before
>
>Changes from v1:
> * Fixed negation on probe time magic matches check to be correct
> * Fixed kernel doc and renamed magic_num to magic
> * Killed cmd_db_get_header_by_rsc_id() entirely
> * Changed chars to u8s for simplicity of thinking about signedness
> * Fixed cmd_db_get_header()'s memcmp to do the right thing by checking
>   for a match instead of the opposite
> * Tested on real hardware
>
> drivers/soc/qcom/cmd-db.c | 131 ++++++++++++++++++++------------------
> 1 file changed, 69 insertions(+), 62 deletions(-)
>
>diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c
>index b5172049f608..a6f646295f06 100644
>--- a/drivers/soc/qcom/cmd-db.c
>+++ b/drivers/soc/qcom/cmd-db.c
>@@ -13,18 +13,9 @@
>
> #define NUM_PRIORITY		2
> #define MAX_SLV_ID		8
>-#define CMD_DB_MAGIC		0x0C0330DBUL
> #define SLAVE_ID_MASK		0x7
> #define SLAVE_ID_SHIFT		16
>
>-#define ENTRY_HEADER(hdr)	((void *)cmd_db_header +	\
>-				sizeof(*cmd_db_header) +	\
>-				hdr->header_offset)
>-
>-#define RSC_OFFSET(hdr, ent)	((void *)cmd_db_header +	\
>-				sizeof(*cmd_db_header) +	\
>-				hdr.data_offset + ent.offset)
>-
> /**
>  * struct entry_header: header for each entry in cmddb
>  *
>@@ -35,11 +26,11 @@
>  * @offset: offset from :@data_offset, start of the data
>  */
> struct entry_header {
>-	u64 id;
>-	u32 priority[NUM_PRIORITY];
>-	u32 addr;
>-	u16 len;
>-	u16 offset;
>+	u8 id[8];
>+	__le32 priority[NUM_PRIORITY];
>+	__le32 addr;
>+	__le16 len;
>+	__le16 offset;
> };
>
> /**
>@@ -53,30 +44,30 @@ struct entry_header {
>  * @reserved: reserved for future use.
>  */
> struct rsc_hdr {
>-	u16 slv_id;
>-	u16 header_offset;
>-	u16 data_offset;
>-	u16 cnt;
>-	u16 version;
>-	u16 reserved[3];
>+	__le16 slv_id;
>+	__le16 header_offset;
>+	__le16 data_offset;
>+	__le16 cnt;
>+	__le16 version;
>+	__le16 reserved[3];
> };
>
> /**
>  * struct cmd_db_header: The DB header information
>  *
>  * @version: The cmd db version
>- * @magic_number: constant expected in the database
>+ * @magic: constant expected in the database
>  * @header: array of resources
>  * @checksum: checksum for the header. Unused.
>  * @reserved: reserved memory
>  * @data: driver specific data
>  */
> struct cmd_db_header {
>-	u32 version;
>-	u32 magic_num;
>+	__le32 version;
>+	u8 magic[4];
> 	struct rsc_hdr header[MAX_SLV_ID];
>-	u32 checksum;
>-	u32 reserved;
>+	__le32 checksum;
>+	__le32 reserved;
> 	u8 data[];
> };
>
>@@ -99,8 +90,34 @@ struct cmd_db_header {
>  * h/w accelerator and request a resource state.
>  */
>
>+static const u8 CMD_DB_MAGIC[] = { 0xdb, 0x30, 0x03, 0x0c };
>+
>+static bool cmd_db_magic_matches(const struct cmd_db_header *header)
>+{
>+	const u8 *magic = header->magic;
>+
>+	return memcmp(magic, CMD_DB_MAGIC, ARRAY_SIZE(CMD_DB_MAGIC)) == 0;
>+}
>+
> static struct cmd_db_header *cmd_db_header;
>
>+
>+static inline void *rsc_to_entry_header(struct rsc_hdr *hdr)
>+{
>+	u16 offset = le16_to_cpu(hdr->header_offset);
>+
>+	return cmd_db_header->data + offset;
>+}
>+
>+static inline void *
>+rsc_offset(struct rsc_hdr *hdr, struct entry_header *ent)
>+{
>+	u16 offset = le16_to_cpu(hdr->data_offset);
>+	u16 loffset = le16_to_cpu(ent->offset);
>+
>+	return cmd_db_header->data + offset + loffset;
>+}
>+
> /**
>  * cmd_db_ready - Indicates if command DB is available
>  *
>@@ -110,29 +127,20 @@ int cmd_db_ready(void)
> {
> 	if (cmd_db_header == NULL)
> 		return -EPROBE_DEFER;
>-	else if (cmd_db_header->magic_num != CMD_DB_MAGIC)
>+	else if (!cmd_db_magic_matches(cmd_db_header))
> 		return -EINVAL;
>
> 	return 0;
> }
> EXPORT_SYMBOL(cmd_db_ready);
>
>-static u64 cmd_db_get_u64_id(const char *id)
>-{
>-	u64 rsc_id = 0;
>-	u8 *ch = (u8 *)&rsc_id;
>-
>-	strncpy(ch, id, min(strlen(id), sizeof(rsc_id)));
>-
>-	return rsc_id;
>-}
>-
>-static int cmd_db_get_header(u64 query, struct entry_header *eh,
>+static int cmd_db_get_header(const char *id, struct entry_header *eh,
> 			     struct rsc_hdr *rh)
> {
> 	struct rsc_hdr *rsc_hdr;
> 	struct entry_header *ent;
> 	int ret, i, j;
>+	u8 query[8];
>
> 	ret = cmd_db_ready();
> 	if (ret)
>@@ -141,18 +149,21 @@ static int cmd_db_get_header(u64 query, struct entry_header *eh,
> 	if (!eh || !rh)
> 		return -EINVAL;
>
>+	/* Pad out query string to same length as in DB */
>+	strncpy(query, id, sizeof(query));
>+
> 	for (i = 0; i < MAX_SLV_ID; i++) {
> 		rsc_hdr = &cmd_db_header->header[i];
> 		if (!rsc_hdr->slv_id)
> 			break;
>
>-		ent = ENTRY_HEADER(rsc_hdr);
>-		for (j = 0; j < rsc_hdr->cnt; j++, ent++) {
>-			if (ent->id == query)
>+		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 < rsc_hdr->cnt) {
>+		if (j < le16_to_cpu(rsc_hdr->cnt)) {
> 			memcpy(eh, ent, sizeof(*ent));
> 			memcpy(rh, rsc_hdr, sizeof(*rh));
> 			return 0;
>@@ -162,15 +173,6 @@ static int cmd_db_get_header(u64 query, struct entry_header *eh,
> 	return -ENODEV;
> }
>
>-static int cmd_db_get_header_by_rsc_id(const char *id,
>-				       struct entry_header *ent_hdr,
>-				       struct rsc_hdr *rsc_hdr)
>-{
>-	u64 rsc_id = cmd_db_get_u64_id(id);
>-
>-	return cmd_db_get_header(rsc_id, ent_hdr, rsc_hdr);
>-}
>-
> /**
>  * cmd_db_read_addr() - Query command db for resource id address.
>  *
>@@ -187,9 +189,9 @@ u32 cmd_db_read_addr(const char *id)
> 	struct entry_header ent;
> 	struct rsc_hdr rsc_hdr;
>
>-	ret = cmd_db_get_header_by_rsc_id(id, &ent, &rsc_hdr);
>+	ret = cmd_db_get_header(id, &ent, &rsc_hdr);
>
>-	return ret < 0 ? 0 : ent.addr;
>+	return ret < 0 ? 0 : le32_to_cpu(ent.addr);
> }
> EXPORT_SYMBOL(cmd_db_read_addr);
>
>@@ -207,19 +209,21 @@ 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;
>+	u16 ent_len;
>
> 	if (!data)
> 		return -EINVAL;
>
>-	ret = cmd_db_get_header_by_rsc_id(id, &ent, &rsc_hdr);
>+	ret = cmd_db_get_header(id, &ent, &rsc_hdr);
> 	if (ret)
> 		return ret;
>
>-	if (len < 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);
>+	len = min_t(u16, ent_len, len);
>+	memcpy(data, rsc_offset(&rsc_hdr, &ent), len);
>
> 	return len;
> }
>@@ -238,9 +242,9 @@ size_t cmd_db_read_aux_data_len(const char *id)
> 	struct entry_header ent;
> 	struct rsc_hdr rsc_hdr;
>
>-	ret = cmd_db_get_header_by_rsc_id(id, &ent, &rsc_hdr);
>+	ret = cmd_db_get_header(id, &ent, &rsc_hdr);
>
>-	return ret < 0 ? 0 : ent.len;
>+	return ret < 0 ? 0 : le16_to_cpu(ent.len);
> }
> EXPORT_SYMBOL(cmd_db_read_aux_data_len);
>
>@@ -256,11 +260,14 @@ enum cmd_db_hw_type cmd_db_read_slave_id(const char *id)
> 	int ret;
> 	struct entry_header ent;
> 	struct rsc_hdr rsc_hdr;
>+	u32 addr;
>
>-	ret = cmd_db_get_header_by_rsc_id(id, &ent, &rsc_hdr);
>+	ret = cmd_db_get_header(id, &ent, &rsc_hdr);
>+	if (ret < 0)
>+		return CMD_DB_HW_INVALID;
>
>-	return ret < 0 ? CMD_DB_HW_INVALID :
>-		       (ent.addr >> SLAVE_ID_SHIFT) & SLAVE_ID_MASK;
>+	addr = le32_to_cpu(ent.addr);
>+	return (addr >> SLAVE_ID_SHIFT) & SLAVE_ID_MASK;
> }
> EXPORT_SYMBOL(cmd_db_read_slave_id);
>
>@@ -282,7 +289,7 @@ static int cmd_db_dev_probe(struct platform_device *pdev)
> 		return ret;
> 	}
>
>-	if (cmd_db_header->magic_num != CMD_DB_MAGIC) {
>+	if (!cmd_db_magic_matches(cmd_db_header)) {
> 		dev_err(&pdev->dev, "Invalid Command DB Magic\n");
> 		return -EINVAL;
> 	}
>--
>Sent by a computer through tubes
>

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