Re: [PATCH] Revert "backlight: pwm: Handle EPROBE_DEFER while requesting the PWM"
From: Robert Jarzmik <robert.jarzmik@free.fr>
Date: 2015-10-01 09:11:49
Also in:
linux-pwm, lkml
Nicolas Ferre [off-list ref] writes:
Le 30/09/2015 21:29, Robert Jarzmik a écrit :quoted
Robert Jarzmik [off-list ref] writes:quoted
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 = 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 = PTR_ERR(pb->pwm); dev_info(&pdev->dev, "%s:%d(): %d\n", __func__, __LINE__, ret); if (ret = -EPROBE_DEFER) goto err_alloc; dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n"); pb->legacy = true; pb->pwm = 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 <robert.jarzmik@free.fr>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) here: 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.
quoted hunk
Otherwise, Boris proposed this fix: 8<-----------------------------------------------------------diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_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_device *pdev) pb->pwm = devm_pwm_get(&pdev->dev, NULL); if (IS_ERR(pb->pwm)) { ret = PTR_ERR(pb->pwm); - if (ret = -EPROBE_DEFER) - goto err_alloc; dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n"); pb->legacy = true; pb->pwm = pwm_request(data->pwm_id, "pwm-backlight"); if (IS_ERR(pb->pwm)) { dev_err(&pdev->dev, "unable to request legacy PWM\n"); - ret = PTR_ERR(pb->pwm); + if (ret != -EPROBE_DEFER) + ret = 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 instead of the revert. If no patch is posted, I maintain my Revert, as this patch _does_ break platforms (omap is broken too AFAICS). Cheers. -- 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 mail ? 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 than the Revert), I NAK the NAK. There is a breakage introduced, and I consider it a strong enough reason to be maintained for the -rc serie.