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Mon, 14 Jul 2025 02:42:17 -0700 (PDT) X-Google-Smtp-Source: AGHT+IG5V4Ve8BAPt6NU+cG8lX/fpEurIJIrdqdQxfcQNaUpGgaXzhyffw4d2Lxh8B67YSliB2bm2g== X-Received: by 2002:a05:6000:e0a:b0:3a4:e841:b236 with SMTP id ffacd0b85a97d-3b5f18cebeemr8726599f8f.33.1752486137180; Mon, 14 Jul 2025 02:42:17 -0700 (PDT) Received: from localhost ([89.128.88.54]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-455ef31717dsm91187365e9.6.2025.07.14.02.42.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Jul 2025 02:42:16 -0700 (PDT) From: Javier Martinez Canillas To: Thomas Zimmermann , linux-kernel@vger.kernel.org Cc: ipedrosa@redhat.com, David Airlie , Maarten Lankhorst , Marcus Folkesson , Maxime Ripard , Simona Vetter , dri-devel@lists.freedesktop.org Subject: Re: [PATCH 2/3] drm/sitronix/st7571-i2c: Make the reset GPIO to be optional In-Reply-To: <10bb159a-0c6a-4950-b038-68608e2a771d@suse.de> References: <20250710102453.101078-1-javierm@redhat.com> <20250710102453.101078-3-javierm@redhat.com> <10bb159a-0c6a-4950-b038-68608e2a771d@suse.de> Date: Mon, 14 Jul 2025 11:42:15 +0200 Message-ID: <87zfd7cdmw.fsf@minerva.mail-host-address-is-not-set> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Thomas Zimmermann writes: Hello Thomas, > Hi > > Am 10.07.25 um 12:24 schrieb Javier Martinez Canillas: >> Some Sitronix LCD controllers (such as the ST7567) don't have a reset pin, >> so lets relax this in the driver and make the reset GPIO to be optional. >> >> The devm_gpiod_get_optional() helper is similar to devm_gpiod_get(), but >> returns NULL when there isn't a reset-gpios property defined in a DT node. >> >> The DT binding schema for "sitronix,st7571" that require a reset GPIO will >> enforce the "reset-gpios" to be present, due being a required DT property. >> But in the driver itself the property can be made optional if not defined. >> >> Signed-off-by: Javier Martinez Canillas >> --- >> >> drivers/gpu/drm/sitronix/st7571-i2c.c | 8 ++++++-- >> 1 file changed, 6 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/gpu/drm/sitronix/st7571-i2c.c b/drivers/gpu/drm/sitronix/st7571-i2c.c >> index eec846892962..73e8db25f895 100644 >> --- a/drivers/gpu/drm/sitronix/st7571-i2c.c >> +++ b/drivers/gpu/drm/sitronix/st7571-i2c.c >> @@ -802,15 +802,19 @@ static int st7571_parse_dt(struct st7571_device *st7571) >> st7571->nlines = dt.vactive.typ; >> st7571->ncols = dt.hactive.typ; >> >> - st7571->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH); >> + st7571->reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH); >> if (IS_ERR(st7571->reset)) >> - return PTR_ERR(st7571->reset); >> + return dev_err_probe(dev, PTR_ERR(st7571->reset), >> + "Failed to get reset gpio\n"); >> >> return 0; >> } >> >> static void st7571_reset(struct st7571_device *st7571) >> { >> + if (!st7571->reset) >> + return; >> + > > My interpretation of this function is that calling it guarantees a > device reset (or an error). So I'd push this test into the caller. > That's a good point. I'll then do the check in the caller. Actually... at the end I didn't need a st7571_reset() call for ST7567 since it has its own struct st7571_panel_data .init callback function. So I can just drop the test for st7571->reset being NULL. -- Best regards, Javier Martinez Canillas Core Platforms Red Hat