linux-kernel - Re: [PATCH v3 1/2] staging: r8188eu: Use usb_control_msg_recv/send() in usbctrl

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Message-ID: <YSepDdf+nHekuIxA@kroah.com>
Date:   Thu, 26 Aug 2021 16:45:33 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Cc:     Larry Finger <Larry.Finger@...inger.net>,
        Phillip Potter <phil@...lpotter.co.uk>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Pavel Skripkin <paskripkin@...il.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: Re: [PATCH v3 1/2] staging: r8188eu: Use usb_control_msg_recv/send()
 in usbctrl_vendorreq()

On Thu, Aug 26, 2021 at 04:24:35PM +0200, Fabio M. De Francesco wrote:
> On Thursday, August 26, 2021 12:48:37 PM CEST Greg Kroah-Hartman wrote:
> > On Wed, Aug 25, 2021 at 05:53:10AM +0200, Fabio M. De Francesco wrote:
> > > Replace usb_control_msg() with the new usb_control_msg_recv() and
> > > usb_control_msg_send() API of USB Core in usbctrl_vendorreq().
> > > Remove no more needed variables. Move out of an if-else block
> > > some code that it is no more dependent on status < 0. Remove
> > > redundant code depending on status > 0 or status == len.
> > > 
> > > Suggested-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
> > > ---
> > > 
> > > v2->v3: Restore the test for success of usb_control_message_recv/send
> > > that was inadvertently removed. Issue reported by Pavel Skripkin.
> > > 
> > > v1->v2: According to suggestions by Christophe JAILLET 
> > > <christophe.jaillet@...adoo.fr>, remove 'pipe' and pass an explicit 0
> > > to the new API. According to suggestions by Pavel Skripkin 
> > > <paskripkin@...il.com>, remove an extra if-else that is no more needed, 
> > > since status can be 0 and < 0 and there is no 3rd state, like it was before.
> > > Many thanks to them and also to Phillip Potter <phil@...lpotter.co.uk>
> > > who kindly offered his time for the purpose of testing v1.
> > > 
> > >  drivers/staging/r8188eu/hal/usb_ops_linux.c | 45 ++++++++-------------
> > >  1 file changed, 17 insertions(+), 28 deletions(-)
> > 
> > This doesn't apply to my tree at all.  Please rebase and resend.
> 
> This series cannot apply to your tree until another one of mine is applied 
> ("staging: r8188eu: Remove _enter/_exit_critical_mutex()"). This series builds
> on the previous patch.

When you do that, please let me know somehow that this is the case,
otherwise how am I supposed to guess that?

> > But first, are you sure you want to use these new functions here?  This
> > is a "common" function that is called from different places for
> > different things.  How about unwinding the callers of this function
> > first, to see if they really need all of the complexity in this function
> > at all, and if not, then call the real USB function in those locations
> > instead.
> 
> I think it could be fine to simply refactor usbctrl_vendorreq() to use the newer
> API with no necessity to directly use them at least in six different places in
> hal/usb_ops_linux.c. The only users of this helper are usb_read8/16/32() and
> usb_write8/16/32(). Why do you prefer using usb_control_msg_recv/send() 
> directly in the callers? I guess it would lead to redundant code, more or less
> the same code repeated again and again within the above-mentioned six callers.
> What do we improve by doing as you suggest? What am I missing?

If you unwind the mess, you will find that the code will be much easier
to understand.

As an example, look at usb_write8().  Where is it ever called?  Why do
we have it at all?  It's only used in 1 place, and then that function
unwinds into rtw_write8(), which is used in a lot of places, and never
checked at all, making the majority of the logic in this function
totally unneeded and useless.

Same for rtw_write16() and rtw_write32().  After unwinding the mess you
see that the logic you are working to try to clean up in this patch
series is pretty much not used / needed at all, right?  So why do it?

Unwind the mess into a useful set of functions the driver can actually
call that is not 2-4 function pointers deep and then we can talk about
unifying things, if they are really needed.  But right now, it's
impossible to tell.

good luck!

greg k-h