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Mon, 29 Apr 2024 17:00:41 +0200 Date: Mon, 29 Apr 2024 17:00:41 +0200 From: Johan Hovold To: Srinivas Kandagatla Cc: broonie@kernel.org, perex@perex.cz, tiwai@suse.com, lgirdwood@gmail.com, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, Bjorn Andersson Subject: Re: [PATCH v2 0/4] ASoC: qcom: display port changes Message-ID: References: <20240422134354.89291-1-srinivas.kandagatla@linaro.org> <92b02fd3-5eba-42a7-a166-21b14724b10c@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Message-ID-Hash: K5CTPXDR6Y4F6ES4DSKPUDCYXRHDHSMN X-Message-ID-Hash: K5CTPXDR6Y4F6ES4DSKPUDCYXRHDHSMN X-MailFrom: johan@kernel.org X-Mailman-Rule-Hits: nonmember-moderation X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-alsa-devel.alsa-project.org-0; header-match-alsa-devel.alsa-project.org-1 X-Mailman-Version: 3.3.9 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Tue, Apr 23, 2024 at 04:59:56PM +0100, Srinivas Kandagatla wrote: > On 23/04/2024 15:58, Johan Hovold wrote: > >> It is absolutely possible to run all the streams in parallel from the > >> Audio hardware and DSP point of view. > >> > >> One thing to note is, On Qualcomm DP IP, we can not read/write registers > >> if the DP port is not connected, which means that we can not send data > >> in such cases. > >> > >> This makes it challenging to work with sound-servers like pipewire or > >> pulseaudio as they tend to send silence data at very early stages in the > >> full system boot up, ignoring state of the Jack events. > > This bit sounds like it can and should be worked around by the driver to > > avoid hard-coding policy which would prevent use cases such as the ones > > mentioned above. > This is not simple as you say. We have to fit these into a proper DPCM. > Either we have a dummy Backend connected for each of these pcm > sub-devices when DP port is not connected and then switch back to DP > when its connected. I don't know how best to implement it, but we shouldn't necessarily let that determine the user experience. > Or somehow find a way to not let the pipewire talk to devices which are > not connected. Yes, perhaps it requires a change in user space. But it seems the kernel should be able to fake whatever probing user space currently does to determine if the there is a DP jack (even when there is nothing connected). Johan