Re: [PATCH 2/7] firmware: add offset to request_firmware_into_buf

From: Scott Branden
Date: Mon Aug 26 2019 - 13:24:28 EST

Hi Takashi,

On 2019-08-26 10:12 a.m., Takashi Iwai wrote:
On Mon, 26 Aug 2019 17:41:40 +0200,
Scott Branden wrote:
HI Takashi,

On 2019-08-26 8:20 a.m., Takashi Iwai wrote:
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 with fallbacks.
But how? You patch doesn't change anything about the fallback loading
Correct - I didn't change any of the underlying mechanisms,
so however request_firmware_into_buf worked before it still does.
Or, if the expected behavior is to load the whole content
and then copy a part, what's the merit of this API?
The merit of the API is that the entire file is not copied into a buffer.
In my use case, the buffer is a memory region in PCIe space that isn't
even large enough for the whole file. So the only way to get the file
is to read it
in portions.
BTW: does the use case above mean that the firmware API directly
writes onto the given PCI iomem region? If so, I'm not sure whether
it would work as expected on all architectures. There must be a
reason of the presence of iomem-related API like memcpy_toio()...
Yes, we access the PCI region directly in the driver and thus also through request_firmware_into_buf.
I will admit I am not familiar with every subtlety of PCI accesses. Any comments to the Valkyrie driver in this patch series are appreciated.
But not all drivers need to work on all architectures. I can add a depends on x86 64bit architectures to the driver to limit it to such.