linux-kernel - Re: [PATCH] staging: media: atomisp: refactor sizeof(struct type) to sizeof(*ptr)

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Message-ID: <CAF6CsJwg8EFtCT+zyKWex=RbWu4TyZanbXnqip=J7=sCZDab5Q@mail.gmail.com>
Date: Tue, 13 Jan 2026 16:07:02 +0530
From: Anubhav Kokane <dev.anubhavk@...il.com>
To: Andy Shevchenko <andriy.shevchenko@...el.com>
Cc: hansg@...nel.org, mchehab@...nel.org, andy@...nel.org, 
	sakari.ailus@...ux.intel.com, gregkh@...uxfoundation.org, 
	linux-media@...r.kernel.org, linux-staging@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: media: atomisp: refactor sizeof(struct type) to sizeof(*ptr)

On Tue, Jan 13, 2026 at 12:44 AM Andy Shevchenko  wrote:
> the preferred way is to switch to use kcalloc() in all three places.
>
>                 x = kcalloc(count, sizeof(*...), ...);
>                 if (!x)
>                         ...handle error...
>
>                 while (count--) {
>                         ...
>                 }
>                 ...
> err:
>                 list_for_each... {
>                         ...
>                 }
>                 kfree(x);
>
Hi Andy,
Thank you for the feedback.
I looked into implementing kcalloc() as suggested. But the issue is struct
atomisp_s3a_buf (and the other buffers) are defined as list nodes with
struct list_head list embedded in them. The driver relies on adding these
individually to asd->s3a_stats and freeing them individually using kfree()
in multiple cleanup paths (including error path here).

Switching to kcalloc() would mean the s3a_buf is no longer a standalone
object but a slice of an array. This would lead to invalid or double frees
if the existing code tries kfree() on this array element.

Addressing this requires a larger refactor of the buffer management logic
across the driver, would you prefer I stick to the sizeof(*ptr) hardening for
now to fix the checkpatch warning?

Regards,
Anubhav