linux-kernel - Re: [PATCH 01/23] uvc: Replace memcpy with struct assignment

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Date:	Thu, 27 Dec 2012 18:12:46 -0300
From:	Ezequiel Garcia <elezegarcia@...il.com>
To:	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Cc:	Julia.Lawall@...6.fr, kernel-janitors@...r.kernel.org,
	Ezequiel Garcia <elezegarcia@...il.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Peter Senna Tschudin <peter.senna@...il.com>,
	Mauro Carvalho Chehab <mchehab@...hat.com>
Subject: Re: [PATCH 01/23] uvc: Replace memcpy with struct assignment

Mauro,

On Tue, Oct 23, 2012 at 4:57 PM, Ezequiel Garcia <elezegarcia@...il.com> wrote:
> This kind of memcpy() is error-prone. Its replacement with a struct
> assignment is prefered because it's type-safe and much easier to read.
>
> Found by coccinelle. Hand patched and reviewed.
> Tested by compilation only.
>
> A simplified version of the semantic match that finds this problem is as
> follows: (http://coccinelle.lip6.fr/)
>
> // <smpl>
> @@
> identifier struct_name;
> struct struct_name to;
> struct struct_name from;
> expression E;
> @@
> -memcpy(&(to), &(from), E);
> +to = from;
> // </smpl>
>
> Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Signed-off-by: Peter Senna Tschudin <peter.senna@...il.com>
> Signed-off-by: Ezequiel Garcia <elezegarcia@...il.com>
> ---
>  drivers/media/usb/uvc/uvc_v4l2.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> index f00db30..4fc8737 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -314,7 +314,7 @@ static int uvc_v4l2_set_format(struct uvc_streaming *stream,
>                 goto done;
>         }
>
> -       memcpy(&stream->ctrl, &probe, sizeof probe);
> +       stream->ctrl = probe;
>         stream->cur_format = format;
>         stream->cur_frame = frame;
>
> @@ -386,7 +386,7 @@ static int uvc_v4l2_set_streamparm(struct uvc_streaming *stream,
>                 return -EBUSY;
>         }
>
> -       memcpy(&probe, &stream->ctrl, sizeof probe);
> +       probe = stream->ctrl;
>         probe.dwFrameInterval =
>                 uvc_try_frame_interval(stream->cur_frame, interval);
>
> @@ -397,7 +397,7 @@ static int uvc_v4l2_set_streamparm(struct uvc_streaming *stream,
>                 return ret;
>         }
>
> -       memcpy(&stream->ctrl, &probe, sizeof probe);
> +       stream->ctrl = probe;
>         mutex_unlock(&stream->mutex);
>
>         /* Return the actual frame period. */
> --
> 1.7.4.4
>

It seems you've marked this one as "Changes requested" [1].
However, Laurent didn't request any change,
but just pointed out we missed one memcpy replacement candidate.

I believe it's safe to apply the patch (together with the other 20 patches)
and we can fix the missing spot in another patch.

Thanks,

-- 
    Ezequiel

[1] http://patchwork.linuxtv.org/patch/15142/
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