linux-kernel - Re: [PATCH v2.5 2/3] firmware: Add support for loading compressed files

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Message-ID: <20190620081003.GA21685@kroah.com>
Date:   Thu, 20 Jun 2019 10:10:03 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Shuah Khan <shuah@...nel.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2.5 2/3] firmware: Add support for loading compressed
 files

On Thu, Jun 20, 2019 at 09:36:03AM +0200, Takashi Iwai wrote:
> On Thu, 20 Jun 2019 01:26:47 +0200,
> Luis Chamberlain wrote:
> > 
> > Sorry for the late review... Ah!
> 
> No problem, thanks for review.
> 
> > On Tue, Jun 11, 2019 at 02:26:25PM +0200, Takashi Iwai wrote:
> > > @@ -354,7 +454,12 @@ module_param_string(path, fw_path_para, sizeof(fw_path_para), 0644);
> > >  MODULE_PARM_DESC(path, "customized firmware image search path with a higher priority than default path");
> > >  
> > >  static int
> > > -fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv)
> > > +fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
> > > +			   const char *suffix,
> > > +			   int (*decompress)(struct device *dev,
> > > +					     struct fw_priv *fw_priv,
> > > +					     size_t in_size,
> > > +					     const void *in_buffer))
> > 
> > I *think* this could be cleaner, I'll elaborate below.
> > 
> > > @@ -645,7 +768,13 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
> > >  	if (ret <= 0) /* error or already assigned */
> > >  		goto out;
> > >  
> > > -	ret = fw_get_filesystem_firmware(device, fw->priv);
> > > +	ret = fw_get_filesystem_firmware(device, fw->priv, "", NULL);
> > > +#ifdef CONFIG_FW_LOADER_COMPRESS
> > > +	if (ret == -ENOENT)
> > > +		ret = fw_get_filesystem_firmware(device, fw->priv, ".xz",
> > > +						 fw_decompress_xz);
> > > +#endif
> > 
> > Hrm, and let more #ifdef'ery.
> > 
> > And so if someone wants to add bzip, we'd add yet-another if else on the
> > return value of this call... and yet more #ifdefs.
> > 
> > We already have a list of paths supported. It seems what we need instead
> > is a list of supported suffixes, and a respective structure which then
> > has its set of callbacks for posthandling.
> > 
> > This way, this could all be handled inside fw_get_filesystem_firmware()
> > neatly, and we can just strive towards avoiding #ifdef'ery.
> 
> Yes, I had similar idea.  Actually my plan for multiple compression
> formats was:
> 
> - Move the decompression part into another file, e.g. decompress_xz.c
>   and change in Makefile:
>   firmware_class-$(CONFIG_FW_LOADER_COMPRESS_XZ) += decompress_xz.o
>   
> - Create a table of the extension and the decompression,
> 
>   static struct fw_decompression_table fw_decompressions[] = {
> 	{ "", NULL },
> #ifdef CONFIG_FW_LOADER_COMPRESS_XZ
> 	{ ".xz", fw_decompress_xz },
> #endif
> #ifdef CONFIG_FW_LOADER_COMPRESS_BZIP2
> 	{ ".bz2", fw_decompress_bzip2 },
> #endif
> 	.....
>   };

But why?  Why not just stick with one for now, we don't need a zillion
different formats to start with.  Let's just stick with .xz and that's
it.  There is no need to do anything else for the foreseeable future.

thanks,

greg k-h