linux-kernel - Re: [PATCH] firmware: Don't attempt to allocate zero bytes with vmalloc()

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Message-ID: <CACVXFVOuQosgF+w6k1RH5D360J4pTM-N=quiSCc=GmWt0102rA@mail.gmail.com>
Date:	Tue, 9 Oct 2012 06:56:02 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] firmware: Don't attempt to allocate zero bytes with vmalloc()

On Sat, Oct 6, 2012 at 1:05 AM, Mark Brown
<broonie@...nsource.wolfsonmicro.com> wrote:
> vmalloc() will fail (very loudly) if we try to allocate zero bytes to
> read a zero byte file. Instead report that we successfully read in all
> zero bytes.
>
> It's not immediately obvious to me that this is better than returning an
> error but it seems better to punt the decision about that to the caller
> on the off chance that it's sensible.
>
> Signed-off-by: Mark Brown <broonie@...nsource.wolfsonmicro.com>
> ---
>  drivers/base/firmware_class.c |    5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> index 8154145..a14eb92 100644
> --- a/drivers/base/firmware_class.c
> +++ b/drivers/base/firmware_class.c
> @@ -62,6 +62,11 @@ static bool fw_read_file_contents(struct file *file, struct firmware *fw)
>         char *buf;
>
>         size = fw_file_size(file);
> +       if (size == 0) {
> +               fw->data = NULL;
> +               fw->size = 0;
> +               return true;
> +       }

Considered that zero-length firmware image doesn't make sense for drivers
(callers), maybe it is a insane firmware image, so how about treating it as a
failure?

Thanks,
--
Ming Lei
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