Re: [PATCH] soc: qcom: cmd-db: fix minor version decoding in debugfs output

[Bjorn Andersson <andersson@kernel.org>]

On Mon, Mar 30, 2026 at 11:33:13AM +0530, ALOK TIWARI wrote:
> 
> 
> On 3/30/2026 11:05 AM, Sneh Mankad wrote:
> > > cmd-db encodes the version as major in the high byte and minor in the low
> > > byte. cmd_db_debugfs_dump() prints the full 16 bit value as the minor
> > > version, resulting in incorrect output.
> > > 
> > > Extract minor from the low byte using (version & 0xff).
> > > 
> > > Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
> > There should be a "fixes:" tag added since this is a fix.
> > > ---
> > >   drivers/soc/qcom/cmd-db.c | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c
> > > index 84a75d8c4b70..eed7013c7676 100644
> > > --- a/drivers/soc/qcom/cmd-db.c
> > > +++ b/drivers/soc/qcom/cmd-db.c
> > > @@ -301,7 +301,7 @@ static int cmd_db_debugfs_dump(struct seq_file
> > > *seq, void *p)
> > >           version = le16_to_cpu(rsc->version);
> > >           major = version >> 8;
> > > -        minor = version;
> > > +        minor = version & 0xff;
> > 
> > Minor is already a u8 type, so assigning a u16 type version to u8 type
> > will automatically truncate the higher 8 bits.
> > 
> > Its the same reason why version is right shifted by 8 before being
> > assigned to major variable.
> > 
> > I do not think there would be any difference in output with or without
> > the change, do you have any example?
> 
> 
> Thanks for pointing this out.
> 
> You are right that if minor is of type u8, assigning a u16 value will
> implicitly truncate the upper 8 bits.
> 
> However, the intention of the change is to explicitly extract the minor
> version from the lower byte, since the encoding defines the version as major
> in the high byte and minor in the low byte.
> 

You should say this in your commit message. Don't try to sneak changes
in, describe the actual problem that you're fixing in your commit
messages.

> Using version & 0xff makes the extraction explicit and consistent with how
> major is derived using version >> 8. It improves readability and avoids
> relying on implicit truncation.
> 
> Since this change does not alter functionality and is mainly for clarity and
> consistency I believe a Fixes: tag may not be appropriate.
> I can also drop “fix” from the subject to avoid confusion.
> 

I agree, this isn't a Fixes, because there is no problem in the current
implementation. A change of this kind would merely make the code
somewhat easier to read - but there will be more of it to read...

Regards,
Bjorn

> Thanks,
> Alok