From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert Jarzmik Date: Thu, 01 Oct 2015 09:06:33 +0000 Subject: Re: [PATCH] Revert "backlight: pwm: Handle EPROBE_DEFER while requesting the PWM" Message-Id: <877fn7dkkm.fsf@belgarion.home> List-Id: References: <1443295482-18687-1-git-send-email-robert.jarzmik@free.fr> <87bncjemdk.fsf@belgarion.home> <560CE816.1060307@atmel.com> In-Reply-To: <560CE816.1060307@atmel.com> (Nicolas Ferre's message of "Thu, 1 Oct 2015 10:00:22 +0200") MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: Nicolas Ferre , Boris BREZILLON , Thierry Reding Cc: linux-pwm@vger.kernel.org, Alexandre Belloni , Jingoo Han , Lee Jones , Jean-Christophe Plagniol-Villard , Tomi Valkeinen , linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org Nicolas Ferre writes: > Le 30/09/2015 21:29, Robert Jarzmik a =C3=A9crit : >> Robert Jarzmik writes: >>=20 >>> This reverts commit 68feaca0b13e453aa14ee064c1736202b48b342f. >>> This commit breaks legacy platforms, for which : >>> (a) no pwm table is added (legacy platforms) >>> (b) in this case, in pwm_get(), pmw_lookup_list is empty, and therefore >>> chosen =3D NULL, and therefore pwm_get() returns NULL, and pwm_get= () >>> returns -EPROBE_DEFER >>> (c) as a consequence, this code is unreachable in pwm_bl.c : >>> if (IS_ERR(pb->pwm)) { >>> ret =3D PTR_ERR(pb->pwm); >>> dev_info(&pdev->dev, "%s:%d(): %d\n", __func__, __LINE__, ret); >>> if (ret =3D -EPROBE_DEFER) >>> goto err_alloc; >>> >>> dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n"); >>> pb->legacy =3D true; >>> pb->pwm =3D pwm_request(data->pwm_id, "pwm-backlight"); >>> >>> As this code is unreachable, all legacy platforms relying on pwm_id are >>> broken, amongst which pxa have been tested as broken. >>> >>> Signed-off-by: Robert Jarzmik >> Thierry, would you have a look please ? >> As I said before, all legacy platform relying on pwm_id are broken. I'd = like to >> be sure this lands in the next -rc series. > > Well, as I answered on the linux-pwm mailing-list (I was not in copy) her= e: > http://article.gmane.org/gmane.linux.pwm/2744 > I wonder if it's not easier to fix the platforms and add the pwm tables... No it's not, at least not for a -rc cycle. It's the long term solution you'= re talking about, not the fix one. > Otherwise, Boris proposed this fix: > 8<----------------------------------------------------------- > diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/p= wm_bl.c > index eff379b..00483d4 100644 > --- a/drivers/video/backlight/pwm_bl.c > +++ b/drivers/video/backlight/pwm_bl.c > @@ -273,15 +273,15 @@ static int pwm_backlight_probe(struct platform_devi= ce *pdev) > pb->pwm =3D devm_pwm_get(&pdev->dev, NULL); > if (IS_ERR(pb->pwm)) { > ret =3D PTR_ERR(pb->pwm); > - if (ret =3D -EPROBE_DEFER) > - goto err_alloc; > =20 > dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n"); > pb->legacy =3D true; > pb->pwm =3D pwm_request(data->pwm_id, "pwm-backlight"); > if (IS_ERR(pb->pwm)) { > dev_err(&pdev->dev, "unable to request legacy PWM\n"); > - ret =3D PTR_ERR(pb->pwm); > + if (ret !=3D -EPROBE_DEFER) > + ret =3D PTR_ERR(pb->pwm); > + > goto err_alloc; > } > } > > which is not tested and may add an extra non-valid error log. I can test that, today, it looks an interesting alternative. If both solutions do work, someone (Boris) can post a patch for this -rc in= stead of the revert. If no patch is posted, I maintain my Revert, as this patch _= does_ break platforms (omap is broken too AFAICS). Cheers. --=20 Robert PS: I have not received http://article.gmane.org/gmane.linux.pwm/2744. Is it my mailer or MUA which is broken, ie. was I in the "To:" of the m= ail ? PPS: Sorry to having forgotten to join you to the revert PPPS: As long as an other patch is not submitted to fix the issue (other th= an the Revert), I NAK the NAK. There is a breakage introduced, and I con= sider it a strong enough reason to be maintained for the -rc serie.