linux-kernel - Re: [PATCH 5/5] firmware: add DECLARE_FW_CUSTOM

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Date:   Fri, 16 Dec 2016 11:14:05 +0100
From:   Pavel Machek <pavel@....cz>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     gregkh@...uxfoundation.org, ming.lei@...onical.com,
        daniel.wagner@...-carit.de, teg@...m.no, mchehab@....samsung.com,
        zajec5@...il.com, linux-kernel@...r.kernel.org,
        markivx@...eaurora.org, stephen.boyd@...aro.org,
        broonie@...nel.org, zohar@...ux.vnet.ibm.com, tiwai@...e.de,
        johannes@...solutions.net, chunkeey@...glemail.com,
        hauke@...ke-m.de, jwboyer@...oraproject.org,
        dmitry.torokhov@...il.com, dwmw2@...radead.org, jslaby@...e.com,
        torvalds@...ux-foundation.org, luto@...capital.net,
        fengguang.wu@...el.com, rpurdie@...ys.net,
        j.anaszewski@...sung.com, Abhay_Salunke@...l.com,
        Julia.Lawall@...6.fr, Gilles.Muller@...6.fr, nicolas.palix@...g.fr,
        dhowells@...hat.com, bjorn.andersson@...aro.org,
        arend.vanspriel@...adcom.com, kvalo@...eaurora.org,
        linux-leds@...r.kernel.org
Subject: Re: [PATCH 5/5] firmware: add DECLARE_FW_CUSTOM_FALLBACK() annotation

On Fri 2016-12-16 10:59:06, Luis R. Rodriguez wrote:
> On Fri, Dec 16, 2016 at 10:29:20AM +0100, Pavel Machek wrote:
> > On Fri 2016-12-16 10:22:41, Luis R. Rodriguez wrote:
> > > On Tue, Dec 13, 2016 at 08:04:29PM +0100, Pavel Machek wrote:
> > > > Hi!
> > > > 
> > > > > We need to ensure that when driver developers use the custom firmware
> > > > > fallback mechanism it was not a copy and paste bug. These use cases on
> > > > > upstream drivers are rare, we only have 2 upstream users and its for
> > > > > really old drivers. Since valid uses are rare but possible enable a
> > > > > white-list for its use, and use this same white-list annotation to refer
> > > > > to the documentation covering the custom use case.
> > > > 
> > > > > --- a/drivers/leds/leds-lp55xx-common.c
> > > > > +++ b/drivers/leds/leds-lp55xx-common.c
> > > > > @@ -219,6 +219,7 @@ static void lp55xx_firmware_loaded(const struct firmware *fw, void *context)
> > > > >  	release_firmware(chip->fw);
> > > > >  }
> > > > >  
> > > > > +DECLARE_FW_CUSTOM_FALLBACK("Documentation/leds/leds-lp55xx.txt");
> > > > >  static int lp55xx_request_firmware(struct lp55xx_chip *chip)
> > > > >  {
> > > > >  	const char *name = chip->cl->name;
> > > > 
> > > > The driver does:
> > > > 
> > > > static void lp55xx_firmware_loaded(const struct firmware *fw, void
> > > > *context)
> > > > {
> > > > 	struct lp55xx_chip *chip = context;
> > > > 	        struct device *dev = &chip->cl->dev;
> > > > 		        enum lp55xx_engine_index idx =
> > > > 			chip->engine_idx;
> > > > 
> > > >         if (!fw) {
> > > > 	                dev_err(dev, "firmware request failed\n");
> > > > 			                goto out;
> > > > 					     }
> > > >         ...
> > > > out:
> > > >         /* firmware should be released for other channel use */
> > > > 	        release_firmware(chip->fw);
> > > > }
> > > > 
> > > > 
> > > > Does that match the "custom fallback" definition?
> > > 
> > > Refer to the documentation I supplied, and also to the grammar rule, in
> > > particular the patch "firmware: add SmPL report for custom fallback mechanism",
> > > it captures the SmPL form for the custom fallback mechanism as:
> > 
> > I don't much care what the rule says. If you believe the code is
> > buggy, submit a patch.
> 
> Huh? No, its an old API and valid uses are scarce. The point is to avoid folks
> adding yet other users by mistake by using grammar to help white-list actual
> valid users.

Well, I was asking if the above snipped looks like valid use. Because
AFAICT, the "custom fallback" is just dev_err(), see above. Coccinelle
rules don't help me...
									Pavel

-- 
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