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[2a02:3100:af54:b201:7419:a557:62e9:4d13]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c24967459aesm1547936966b.48.2026.08.24.23.26.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Aug 2026 23:26:33 -0700 (PDT) Date: Tue, 25 Aug 2026 08:26:31 +0200 From: Karl Mehltretter To: Maxime Ripard Cc: Dave Stevenson , =?utf-8?B?TWHDrXJh?= Canal , Raspberry Pi Kernel Maintenance , Maarten Lankhorst , Thomas Zimmermann , David Airlie , Simona Vetter , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm/vc4: hdmi: Unregister the ASoC card on unbind Message-ID: References: <20260822143218.68764-1-kmehltretter@gmail.com> <20260824-expert-sepia-oyster-cabaea@houat> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260824-expert-sepia-oyster-cabaea@houat> On Mon, Aug 24, 2026 at 08:52:44AM +0100, Maxime Ripard wrote: > And that happens only because you have no user. If you had one, you > would have had the opposite sequence. > Hi Maxime, Thanks for the correction, and sorry that v1 described the lifetime too broadly. You are right that DRM-managed memory is released when the last DRM reference is gone, not simply at unbind. With an open DRM fd, vc4_hdmi can outlive platform teardown. v2 was triggered by syzbot comments on the ASoC retry path. A deferred card bind can move the devm registration outside the component devres group. With no DRM fd open, the final DRM release can then free vc4_hdmi before the HDMI platform releases the card. v2 link: https://lore.kernel.org/r/20260823173740.2983-1-kmehltretter@gmail.com/ I will send a v3 based on your input. The implementation change was already in v2. v3 only clarifies the wording and keeps that same implementation. The card is registered without devm and unregistered from component unbind while vc4_hdmi is still alive. I also tested this on a real Pi 400 with /dev/dri/card0 open during vc4-drm sysfs unbind. There were no new KASAN reports. Thanks, Karl