[PATCH] scsi: core: Do not declare scsi_cmnd pointers const

[PATCH] scsi: core: Do not declare scsi_cmnd pointers const

[Bart Van Assche]

This change allows removing multiple casts and hence improves type checking
by the compiler.

Cc: Hannes Reinecke <hare@suse.de>
Suggested-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/scsi_logging.c | 21 ++++++++++-----------
 include/scsi/scsi_dbg.h     |  4 ++--
 include/scsi/scsi_device.h  |  4 ++--
 3 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/drivers/scsi/scsi_logging.c b/drivers/scsi/scsi_logging.c
index b02af340c2d3..3cd0d3074085 100644
--- a/drivers/scsi/scsi_logging.c
+++ b/drivers/scsi/scsi_logging.c
@@ -26,9 +26,9 @@ static void scsi_log_release_buffer(char *bufptr)
 	kfree(bufptr);
 }
 
-static inline const char *scmd_name(const struct scsi_cmnd *scmd)
+static inline const char *scmd_name(struct scsi_cmnd *scmd)
 {
-	struct request *rq = scsi_cmd_to_rq((struct scsi_cmnd *)scmd);
+	const struct request *rq = scsi_cmd_to_rq(scmd);
 
 	if (!rq->q || !rq->q->disk)
 		return NULL;
@@ -80,8 +80,8 @@ void sdev_prefix_printk(const char *level, const struct scsi_device *sdev,
 }
 EXPORT_SYMBOL(sdev_prefix_printk);
 
-void scmd_printk(const char *level, const struct scsi_cmnd *scmd,
-		const char *fmt, ...)
+void scmd_printk(const char *level, struct scsi_cmnd *scmd, const char *fmt,
+		 ...)
 {
 	va_list args;
 	char *logbuf;
@@ -94,7 +94,7 @@ void scmd_printk(const char *level, const struct scsi_cmnd *scmd,
 	if (!logbuf)
 		return;
 	off = sdev_format_header(logbuf, logbuf_len, scmd_name(scmd),
-				 scsi_cmd_to_rq((struct scsi_cmnd *)scmd)->tag);
+				 scsi_cmd_to_rq(scmd)->tag);
 	if (off < logbuf_len) {
 		va_start(args, fmt);
 		off += vscnprintf(logbuf + off, logbuf_len - off, fmt, args);
@@ -371,16 +371,15 @@ void __scsi_print_sense(const struct scsi_device *sdev, const char *name,
 EXPORT_SYMBOL(__scsi_print_sense);
 
 /* Normalize and print sense buffer in SCSI command */
-void scsi_print_sense(const struct scsi_cmnd *cmd)
+void scsi_print_sense(struct scsi_cmnd *cmd)
 {
 	scsi_log_print_sense(cmd->device, scmd_name(cmd),
-			     scsi_cmd_to_rq((struct scsi_cmnd *)cmd)->tag,
-			     cmd->sense_buffer, SCSI_SENSE_BUFFERSIZE);
+			     scsi_cmd_to_rq(cmd)->tag, cmd->sense_buffer,
+			     SCSI_SENSE_BUFFERSIZE);
 }
 EXPORT_SYMBOL(scsi_print_sense);
 
-void scsi_print_result(const struct scsi_cmnd *cmd, const char *msg,
-		       int disposition)
+void scsi_print_result(struct scsi_cmnd *cmd, const char *msg, int disposition)
 {
 	char *logbuf;
 	size_t off, logbuf_len;
@@ -393,7 +392,7 @@ void scsi_print_result(const struct scsi_cmnd *cmd, const char *msg,
 		return;
 
 	off = sdev_format_header(logbuf, logbuf_len, scmd_name(cmd),
-				 scsi_cmd_to_rq((struct scsi_cmnd *)cmd)->tag);
+				 scsi_cmd_to_rq(cmd)->tag);
 
 	if (off >= logbuf_len)
 		goto out_printk;
diff --git a/include/scsi/scsi_dbg.h b/include/scsi/scsi_dbg.h
index bd29cdb513a5..efcdc78530d5 100644
--- a/include/scsi/scsi_dbg.h
+++ b/include/scsi/scsi_dbg.h
@@ -11,11 +11,11 @@ extern size_t __scsi_format_command(char *, size_t,
 				   const unsigned char *, size_t);
 extern void scsi_print_sense_hdr(const struct scsi_device *, const char *,
 				 const struct scsi_sense_hdr *);
-extern void scsi_print_sense(const struct scsi_cmnd *);
+extern void scsi_print_sense(struct scsi_cmnd *);
 extern void __scsi_print_sense(const struct scsi_device *, const char *name,
 			       const unsigned char *sense_buffer,
 			       int sense_len);
-extern void scsi_print_result(const struct scsi_cmnd *, const char *, int);
+extern void scsi_print_result(struct scsi_cmnd *, const char *, int);
 
 #ifdef CONFIG_SCSI_CONSTANTS
 extern bool scsi_opcode_sa_name(int, int, const char **, const char **);
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 6d6500148c4b..4c106342c4ae 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -313,8 +313,8 @@ sdev_prefix_printk(const char *, const struct scsi_device *, const char *,
 #define sdev_printk(l, sdev, fmt, a...)				\
 	sdev_prefix_printk(l, sdev, NULL, fmt, ##a)
 
-__printf(3, 4) void
-scmd_printk(const char *, const struct scsi_cmnd *, const char *, ...);
+__printf(3, 4) void scmd_printk(const char *, struct scsi_cmnd *, const char *,
+				...);
 
 #define scmd_dbg(scmd, fmt, a...)					\
 	do {								\

Re: [PATCH] scsi: core: Do not declare scsi_cmnd pointers const

[John Garry]

On 14/10/2025 23:04, Bart Van Assche wrote:

Maybe mention in the title that we are touching the scsi logging code

> This change allows removing multiple casts and hence improves type checking
> by the compiler.
> 
> Cc: Hannes Reinecke <hare@suse.de>
> Suggested-by: John Garry <john.g.garry@oracle.com>

thanks
Reviewed-by: John Garry <john.g.garry@oracle.com>

> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>   drivers/scsi/scsi_logging.c | 21 ++++++++++-----------
>   include/scsi/scsi_dbg.h     |  4 ++--
>   include/scsi/scsi_device.h  |  4 ++--
>   3 files changed, 14 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_logging.c b/drivers/scsi/scsi_logging.c
> index b02af340c2d3..3cd0d3074085 100644
> --- a/drivers/scsi/scsi_logging.c
> +++ b/drivers/scsi/scsi_logging.c
> @@ -26,9 +26,9 @@ static void scsi_log_release_buffer(char *bufptr)
>   	kfree(bufptr);
>   }
>   
> -static inline const char *scmd_name(const struct scsi_cmnd *scmd)
> +static inline const char *scmd_name(struct scsi_cmnd *scmd)
>   {
> -	struct request *rq = scsi_cmd_to_rq((struct scsi_cmnd *)scmd);
> +	const struct request *rq = scsi_cmd_to_rq(scmd);

do you really need to declare this a pointer to const? Or just a good 
practice?

Re: [PATCH] scsi: core: Do not declare scsi_cmnd pointers const

[Bart Van Assche]

On 10/20/25 4:39 AM, John Garry wrote:
> On 14/10/2025 23:04, Bart Van Assche wrote:
>> diff --git a/drivers/scsi/scsi_logging.c b/drivers/scsi/scsi_logging.c
>> index b02af340c2d3..3cd0d3074085 100644
>> --- a/drivers/scsi/scsi_logging.c
>> +++ b/drivers/scsi/scsi_logging.c
>> @@ -26,9 +26,9 @@ static void scsi_log_release_buffer(char *bufptr)
>>       kfree(bufptr);
>>   }
>> -static inline const char *scmd_name(const struct scsi_cmnd *scmd)
>> +static inline const char *scmd_name(struct scsi_cmnd *scmd)
>>   {
>> -    struct request *rq = scsi_cmd_to_rq((struct scsi_cmnd *)scmd);
>> +    const struct request *rq = scsi_cmd_to_rq(scmd);
> 
> do you really need to declare this a pointer to const? Or just a good 
> practice?

It's a matter of code style. In some code bases the memory a pointer
points at is always declared const if the pointer is not used to modify
that memory. In other code bases, e.g. the Linux kernel, the "const
type *" pattern is not that common.

Thanks,

Bart.

Re: [PATCH] scsi: core: Do not declare scsi_cmnd pointers const

[Martin K. Petersen]

Bart,

> This change allows removing multiple casts and hence improves type
> checking by the compiler.

Applied to 6.19/scsi-staging, thanks!

-- 
Martin K. Petersen