linux-kernel - Re: [PATCH 3/3] soc: qcom: mdt_loader: add offset to request_firmware_into

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Date:   Thu, 22 Aug 2019 12:33:08 -0700
From:   Scott Branden <scott.branden@...adcom.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "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>
Subject: Re: [PATCH 3/3] soc: qcom: mdt_loader: add offset to
 request_firmware_into_buf

Hi Greg,

On 2019-05-23 9:56 a.m., Greg Kroah-Hartman wrote:
> On Thu, May 23, 2019 at 09:41:49AM -0700, Scott Branden wrote:
>> Hi Greg,
>>
>> On 2019-05-22 10:52 p.m., Greg Kroah-Hartman wrote:
>>> On Wed, May 22, 2019 at 07:51:13PM -0700, Scott Branden wrote:
>>>> Adjust request_firmware_into_buf API to allow for portions
>>>> of firmware file to be read into a buffer.  mdt_loader still
>>>> retricts request fo whole file read into buffer.
>>>>
>>>> Signed-off-by: Scott Branden <scott.branden@...adcom.com>
>>>> ---
>>>>    drivers/soc/qcom/mdt_loader.c | 7 +++++--
>>>>    1 file changed, 5 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/soc/qcom/mdt_loader.c b/drivers/soc/qcom/mdt_loader.c
>>>> index 1c488024c698..ad20d159699c 100644
>>>> --- a/drivers/soc/qcom/mdt_loader.c
>>>> +++ b/drivers/soc/qcom/mdt_loader.c
>>>> @@ -172,8 +172,11 @@ static int __qcom_mdt_load(struct device *dev, const struct firmware *fw,
>>>>    		if (phdr->p_filesz) {
>>>>    			sprintf(fw_name + fw_name_len - 3, "b%02d", i);
>>>> -			ret = request_firmware_into_buf(&seg_fw, fw_name, dev,
>>>> -							ptr, phdr->p_filesz);
>>>> +			ret = request_firmware_into_buf
>>>> +						(&seg_fw, fw_name, dev,
>>>> +						 ptr, phdr->p_filesz,
>>>> +						 0,
>>>> +						 KERNEL_PREAD_FLAG_WHOLE);
>>> So, all that work in the first 2 patches for no real change at all?  Why
>>> are these changes even needed?
>> The first two patches allow partial read of files into memory.
>>
>> Existing kernel drivers haven't need such functionality so, yes, there
>> should be no real change
>>
>> with first two patches other than adding such partial file read support.
>>
>> We have a new driver in development which needs partial read of files
>> supported in the kernel.
> As I said before, I can not take new apis without any in-kernel user.
> So let's wait for your new code that thinks it needs this, and then we
> will be glad to evaluate all of this at that point in time.

I have submitted all the necessary patches you requested here.

These include first adding tests for existing API that never had a 
kernel selftest:

https://lkml.org/lkml/2019/8/22/1367

Followed by API enhancement, tests updated, and a new driver requiring 
enhanced API:

https://lkml.org/lkml/2019/8/22/1404

>
> To do so otherwise is to have loads of unused "features" aquiring cruft
> in the kernel source, and you do not want that.
>
> thanks,
>
> greg k-h

Thanks,

Scott