linux-kernel - Re: [PATCH 1/2] driver core: firmware loader: don't cache FW_ACTION

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Date:	Mon, 27 May 2013 14:23:02 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	anish singh <anish198519851985@...il.com>
Cc:	Ming Lei <ming.lei@...onical.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel-mail <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] driver core: firmware loader: don't cache FW_ACTION_NOHOTPLUG firmware

At Mon, 27 May 2013 17:26:22 +0530,
anish singh wrote:
> 
> On Mon, May 27, 2013 at 4:00 PM, Ming Lei <ming.lei@...onical.com> wrote:
> > Generally there are only two drivers which don't need uevent to
> > handle firmware loading, so don't cache these firmwares during
> Sorry but this statement confuses me i.e. "drivers which don't need
> uevent to handle firmware loading". Does this mean that driver is
> dependent on uevent to load the firmware?

No.

> or does this mean
> that driver generates uevent to userspace and userpace in turn
> provides the firmware?

No.

The userspace doesn't require uevent, and the driver doesn't generate
uevent, either.  The userspace just loads the file when ready.
See Documentation/dell_rbu.txt for example.  (And yes, it's a bad
design.)


Takashi

> > suspend for these drivers since doing that may block firmware
> > loading forever.
> Explanation about why would it block would really help me or
> for that matter anyone who reads this commit. Or may be
> a url which discussed this problem.
> >
> > Both the two drivers are involved in private firmware images, so
> > they don't hit in direct loading too.
> >
> > Cc: Takashi Iwai <tiwai@...e.de>
> > Signed-off-by: Ming Lei <ming.lei@...onical.com>
> > ---
> >  drivers/base/firmware_class.c |    9 ++++++---
> >  1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> > index e650c25..64e7870 100644
> > --- a/drivers/base/firmware_class.c
> > +++ b/drivers/base/firmware_class.c
> > @@ -993,7 +993,8 @@ _request_firmware_prepare(struct firmware **firmware_p, const char *name,
> >         return 1; /* need to load */
> >  }
> >
> > -static int assign_firmware_buf(struct firmware *fw, struct device *device)
> > +static int assign_firmware_buf(struct firmware *fw, struct device *device,
> > +                               bool skip_cache)
> >  {
> >         struct firmware_buf *buf = fw->priv;
> >
> > @@ -1010,7 +1011,7 @@ static int assign_firmware_buf(struct firmware *fw, struct device *device)
> >          * device may has been deleted already, but the problem
> >          * should be fixed in devres or driver core.
> >          */
> > -       if (device)
> > +       if (device && !skip_cache)
> >                 fw_add_devm_name(device, buf->fw_id);
> >
> >         /*
> > @@ -1066,8 +1067,10 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
> >         if (!fw_get_filesystem_firmware(device, fw->priv))
> >                 ret = fw_load_from_user_helper(fw, name, device,
> >                                                uevent, nowait, timeout);
> > +
> > +       /* don't cache firmware handled without uevent */
> >         if (!ret)
> > -               ret = assign_firmware_buf(fw, device);
> > +               ret = assign_firmware_buf(fw, device, !uevent);
> >
> >         usermodehelper_read_unlock();
> >
> > --
> > 1.7.9.5
> >
> > --
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