linux-kernel - Re: [PATCH 2/7] firmware: add offset to request_firmware_into

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Date:   Mon, 26 Aug 2019 17:20:52 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Scott Branden <scott.branden@...adcom.com>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        David Brown <david.brown@...aro.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Shuah Khan <shuah@...nel.org>, bjorn.andersson@...aro.org,
        Shuah Khan <skhan@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        Olof Johansson <olof@...om.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Colin Ian King <colin.king@...onical.com>,
        Kees Cook <keescook@...omium.org>,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 2/7] firmware: add offset to request_firmware_into_buf

On Fri, 23 Aug 2019 21:44:42 +0200,
Scott Branden wrote:
> 
> Hi Takashi,
> 
> Thanks for review.  comments below.
> 
> On 2019-08-23 3:05 a.m., Takashi Iwai wrote:
> > On Thu, 22 Aug 2019 21:24:46 +0200,
> > Scott Branden wrote:
> >> Add offset to request_firmware_into_buf to allow for portions
> >> of firmware file to be read into a buffer.  Necessary where firmware
> >> needs to be loaded in portions from file in memory constrained systems.
> > AFAIU, this won't work with the fallback user helper, right?
> Seems to work fine in the fw_run_tests.sh with fallbacks.

But how?  You patch doesn't change anything about the fallback loading
mechanism.  Or, if the expected behavior is to load the whole content
and then copy a part, what's the merit of this API?

> > Also it won't work for the compressed firmware files as-is.
> Although unnecessary, seems to work fine in the fw_run_tests.sh with
> "both" and "xzonly" options.

This looks also suspicious.  Loading a part of the file from the
middle and decompression won't work together, from obvious reasons.

If the test passes, it means that the test itself is more likely
incorrect, I'm afraid.


thanks,

Takashi