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Tue, 25 Feb 2025 16:06:37 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id IQbrIo3qvWdbNwAAD6G6ig (envelope-from ); Tue, 25 Feb 2025 16:06:37 +0000 Message-ID: <28e67cc5-6932-48ac-84ef-93af893b2ed9@suse.de> Date: Tue, 25 Feb 2025 17:06:37 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 2/2] drm/tiny: add driver for Apple Touch Bars in x86 Macs To: Aditya Garg Cc: "andriy.shevchenko@linux.intel.com" , "maarten.lankhorst@linux.intel.com" , "mripard@kernel.org" , "airlied@gmail.com" , "simona@ffwll.ch" , Kerem Karabay , Atharva Tiwari , Aun-Ali Zaidi , Linux Kernel Mailing List , "dri-devel@lists.freedesktop.org" References: <3457BF95-0E50-4B70-86DE-EE5EE95D3ACE@live.com> <4D7C00B4-7B75-4715-8D37-0059B22C030D@live.com> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -4.30 X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; MIME_TRACE(0.00)[0:+]; TO_DN_EQ_ADDR_SOME(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FREEMAIL_TO(0.00)[live.com]; FREEMAIL_ENVRCPT(0.00)[gmail.com,live.com]; RCVD_TLS_ALL(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[linux.intel.com,kernel.org,gmail.com,ffwll.ch,kodeit.net,vger.kernel.org,lists.freedesktop.org]; RCVD_COUNT_TWO(0.00)[2]; RCPT_COUNT_SEVEN(0.00)[11]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,bootlin.com:url,suse.de:mid] X-Spam-Flag: NO X-Spam-Level: Hi Am 25.02.25 um 15:54 schrieb Aditya Garg: [...] >>>> +static int appletbdrm_probe(struct usb_interface *intf, >>>> + const struct usb_device_id *id) >>>> +{ >>>> + struct usb_endpoint_descriptor *bulk_in, *bulk_out; >>>> + struct device *dev = &intf->dev; >>>> + struct appletbdrm_device *adev; >>>> + struct drm_device *drm; >>>> + int ret; >>>> + >>>> + ret = usb_find_common_endpoints(intf->cur_altsetting, &bulk_in, &bulk_out, NULL, NULL); >>>> + if (ret) { >>>> + drm_err(drm, "Failed to find bulk endpoints\n"); >>> This is simply wrong (and in this case even lead to crash in some circumstances). >>> drm_err() may not be used here. That's my point in previous discussions. >>> Independently on the subsystem the ->probe() for the sake of consistency and >>> being informative should only rely on struct device *dev, >> That's never going to work with DRM. There's so much code in a DRM probe function that uses the DRM error functions. >> >> This specific instance here is wrong, as the drm pointer hasn't been initialized. But as soon as it is, it's much better to use drm_err() and friends. It will do the right thing and give consistent output across drivers. >> > Ok so this is actually an interesting case, since I am trying to fix it. To initialise the drm pointer, we need to initialise adev, and to initialise adev, we need to run usb_find_common_endpoints first. So IMO, we cannot use drm_err here, but rather dev_err_probe can be used. Maybe start reading those compiler warnings. They are there for a reason. Your compiler tells you that you are dereferencing an uninitialized pointer, right here: https://elixir.bootlin.com/linux/v6.13.4/source/include/drm/drm_print.h#L586 Clearing that pointer to NULL will fix the error and make drm_err() work. Best regards Thomas >> >>>> + return ret; >>>> + } >>>> + >>>> + adev = devm_drm_dev_alloc(dev, &appletbdrm_drm_driver, struct appletbdrm_device, drm); >>>> + if (IS_ERR(adev)) >>>> + return PTR_ERR(adev); >>>> + >>>> + adev->in_ep = bulk_in->bEndpointAddress; >>>> + adev->out_ep = bulk_out->bEndpointAddress; >>>> + adev->dmadev = dev; >>>> + >>>> + drm = &adev->drm; >>>> + >>>> + usb_set_intfdata(intf, adev); >>>> + >>>> + ret = appletbdrm_get_information(adev); >>>> + if (ret) { >>>> + drm_err(drm, "Failed to get display information\n"); >>>> + return ret; >>>> + } >>>> + >>>> + ret = appletbdrm_signal_readiness(adev); >>>> + if (ret) { >>>> + drm_err(drm, "Failed to signal readiness\n"); >>>> + return ret; >>>> + } >>>> + >>>> + ret = appletbdrm_setup_mode_config(adev); >>>> + if (ret) { >>>> + drm_err(drm, "Failed to setup mode config\n"); >>>> + return ret; >>>> + } >>>> + >>>> + ret = drm_dev_register(drm, 0); >>>> + if (ret) { >>>> + drm_err(drm, "Failed to register DRM device\n"); >>>> + return ret; >>>> + } >>>> + >>>> + ret = appletbdrm_clear_display(adev); >>>> + if (ret) { >>>> + drm_err(drm, "Failed to clear display\n"); >>>> + return ret; >>>> + } >>>> + >>>> + return 0; >>>> +} >> -- >> -- >> Thomas Zimmermann >> Graphics Driver Developer >> SUSE Software Solutions Germany GmbH >> Frankenstrasse 146, 90461 Nuernberg, Germany >> GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman >> HRB 36809 (AG Nuernberg) >> -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)