Re: [PATCH v4 1/1] scsi: ufs: core: add device level exception support

[Bao D. Nguyen]

On 3/26/2025 3:49 AM, Bart Van Assche wrote:
> On 3/25/25 6:15 PM, Bao D. Nguyen wrote:
> > The existing "struct utp_upiu_query_v4_0" probably has a bug in it. It 
> > does not use the  __attribute__((__packed__)) attribute. The compiler 
> > is free to add padding in this structure, resulting in the read 
> > attribute value being incorrect. I plan to provide a separate patch to 
> > fix this issue.
>
> Adding __attribute__((__packed__)) or __packed to data structures that
> don't need it is not an improvement but is a change that makes
> processing slower on architectures that do not support unaligned
> accesses. Instead of adding __packed to data structures in their
> entirety, only add it to those members that need it and check the
> structure size as follows:
>
> static_assert(sizeof(...) == ...);
Thank you for the info on this, Bart.
IMO, this response upiu data should be __packed because the data coming 
from the hardware follows a strict format as defined by the spec. If we 
support __pack each individual field which data may be read by the 
driver (the attribute read commands) and check the validity of their 
sizes, it may add some complexity?

Thanks, Bao