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[2003:e4:1f1c:4d00:f22f:74ff:fe1f:3a53]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45b9c234b24sm59432145e9.16.2025.09.03.08.38.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Sep 2025 08:38:08 -0700 (PDT) Date: Wed, 3 Sep 2025 17:38:06 +0200 From: Thierry Reding To: John Stultz Cc: David Airlie , Simona Vetter , Sumit Semwal , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Benjamin Gaignard , Brian Starkey , "T.J. Mercier" , Andrew Morton , David Hildenbrand , Mike Rapoport , dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, linux-tegra@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org Subject: Re: [PATCH 4/9] dma-buf: heaps: Add debugfs support Message-ID: References: <20250902154630.4032984-1-thierry.reding@gmail.com> <20250902154630.4032984-5-thierry.reding@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="sulytsn4e2thgtl4" Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: B9556140006 X-Stat-Signature: ayaowab6yw5xebof1ez4eo8713cog4ot X-Rspam-User: X-HE-Tag: 1756913891-423855 X-HE-Meta: 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 ob61Q3m5 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: --sulytsn4e2thgtl4 Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH 4/9] dma-buf: heaps: Add debugfs support MIME-Version: 1.0 On Tue, Sep 02, 2025 at 03:37:45PM -0700, John Stultz wrote: > On Tue, Sep 2, 2025 at 8:46=E2=80=AFAM Thierry Reding wrote: > > > > From: Thierry Reding > > > > Add a callback to struct dma_heap_ops that heap providers can implement > > to show information about the state of the heap in debugfs. A top-level > > directory named "dma_heap" is created in debugfs and individual files > > will be named after the heaps. > > >=20 > I know its debugfs, but this feels a little loosey-goosey as an uAPI. Well, the whole point of debugfs is that it's not really an ABI. Nothing should ever rely on the presence of these files. > Is there any expected format for the show function? >=20 > What would other dmabuf heaps ideally export via this interface? I've thought about this a bit and I'm not sure it makes sense to standardize on this. I think on one hand having a list of buffers exported by the dma-buf heap is probably the lowest common denominator, but then there might be a bunch of other things that are very heap- specific that some heap might want to export. > Is there some consistent dma_heap-ish concept for it to justify it > being under a dma_heap directory, and not just an independent debugfs > file for the driver implementing the dmabuf heap? Well, I think just the fact that it's a dma-heap would qualify its corresponding debugfs to be in a well-known location. We could of course pick some arbitrary location, but that's just a recipe for chaos because then everybody puts these whereever they want. There's really no standard place for driver-specific debugfs files to go, so putting it into some "subsystem"-specific directory seems like the better option. 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