Re: [PATCH v5 2/7] firmware: add offset to request_firmware_into_buf

[Scott Branden]

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@xxxxxxxxxxxx>
> > ---
> >   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