linux-kernel - Re: [PATCH v5 2/7] firmware: add offset to request_firmware_into

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Date:   Wed, 13 May 2020 11:35:06 -0700
From:   Scott Branden <scott.branden@...adcom.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     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>,
        Takashi Iwai <tiwai@...e.de>, linux-kselftest@...r.kernel.org,
        Andy Gross <agross@...nel.org>
Subject: Re: [PATCH v5 2/7] firmware: add offset to request_firmware_into_buf

Hi Luis,

Another question.

On 2020-05-12 5:33 p.m., Luis Chamberlain wrote:
> On Thu, May 07, 2020 at 05:27:34PM -0700, 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.
>>
>> Signed-off-by: Scott Branden <scott.branden@...adcom.com>
>> ---
>>   drivers/base/firmware_loader/firmware.h |  5 +++
>>   drivers/base/firmware_loader/main.c     | 52 +++++++++++++++++--------
>>   drivers/soc/qcom/mdt_loader.c           |  7 +++-
>>   include/linux/firmware.h                |  8 +++-
>>   lib/test_firmware.c                     |  4 +-
>>   5 files changed, 55 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/base/firmware_loader/firmware.h b/drivers/base/firmware_loader/firmware.h
>> index 25836a6afc9f..1147dae01148 100644
>> --- a/drivers/base/firmware_loader/firmware.h
>> +++ b/drivers/base/firmware_loader/firmware.h
>> @@ -32,6 +32,8 @@
>>    * @FW_OPT_FALLBACK_PLATFORM: Enable fallback to device fw copy embedded in
>>    *	the platform's main firmware. If both this fallback and the sysfs
>>    *      fallback are enabled, then this fallback will be tried first.
>> + * @FW_OPT_PARTIAL: Allow partial read of firmware instead of needing to read
>> + *	entire file.
> See, this allows us use kdoc to document his nicely. Do that with the
> kernel pread stuff.
>
>> @@ -68,6 +71,8 @@ struct fw_priv {
>>   	void *data;
>>   	size_t size;
>>   	size_t allocated_size;
>> +	size_t offset;
>> +	unsigned int flags;
> But flags is a misnomer, you just do two operations, just juse an enum
> here to classify the read operation.
>
>> index 76f79913916d..4552b7bb819f 100644
>> --- a/drivers/base/firmware_loader/main.c
>> +++ b/drivers/base/firmware_loader/main.c
>> @@ -167,7 +167,8 @@ static int fw_cache_piggyback_on_request(const char *name);
>>   
>>   static struct fw_priv *__allocate_fw_priv(const char *fw_name,
>>   					  struct firmware_cache *fwc,
>> -					  void *dbuf, size_t size)
>> +					  void *dbuf, size_t size,
>> +					  size_t offset, unsigned int flags)
> And likewise just use an enum here too.
>
>> @@ -210,9 +213,11 @@ static struct fw_priv *__lookup_fw_priv(const char *fw_name)
>>   static int alloc_lookup_fw_priv(const char *fw_name,
>>   				struct firmware_cache *fwc,
>>   				struct fw_priv **fw_priv, void *dbuf,
>> -				size_t size, enum fw_opt opt_flags)
>> +				size_t size, enum fw_opt opt_flags,
>> +				size_t offset)
> flags? But its a single variable enum!
fw_opt is an existing enum which doesn't really act like an enum.
It is a series of BIT defines in an enum that are then OR'd together in 
the (existing) code?
>
>>   {
>>   	struct fw_priv *tmp;
>> +	unsigned int pread_flags;
>>   
>>   	spin_lock(&fwc->lock);
>>   	if (!(opt_flags & FW_OPT_NOCACHE)) {
Have a look here - enum used as series of flags.
>> @@ -226,7 +231,12 @@ static int alloc_lookup_fw_priv(const char *fw_name,
>>   		}
>>   	}
>>   
>> -	tmp = __allocate_fw_priv(fw_name, fwc, dbuf, size);
>> +	if (opt_flags & FW_OPT_PARTIAL)
>> +		pread_flags = KERNEL_PREAD_FLAG_PART;
>> +	else
>> +		pread_flags = KERNEL_PREAD_FLAG_WHOLE;
>> +
>> +	tmp = __allocate_fw_priv(fw_name, fwc, dbuf, size, offset, pread_flags);
> One of the advantages of using an enum is that you can then use a switch
> here, and the compiler will warn if you haven't handled all the cases.
pread_flags is currently such.  I will change to enum pread_opt.
>
>>   		/* load firmware files from the mount namespace of init */
>> -		rc = kernel_read_file_from_path_initns(path, &buffer,
>> -						       &size, msize, id);
>> +		rc = kernel_pread_file_from_path_initns(path, &buffer,
>> +							&size, fw_priv->offset,
>> +							msize,
>> +							fw_priv->flags, id);
> And here you'd just pass the kernel enum.
Yes, will change to fw_priv->opt and use enum for this one.
>
> You get the idea, I stopped reviewing after this.
>
>    Luis