From: Jason Gunthorpe <jgg@ziepe.ca>
To: "Christian König" <christian.koenig@amd.com>
Cc: Karl Mehltretter <kmehltretter@gmail.com>,
Gerd Hoffmann <kraxel@redhat.com>,
Vivek Kasireddy <vivek.kasireddy@intel.com>,
Sumit Semwal <sumit.semwal@linaro.org>,
dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org,
linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] udmabuf: respect the device's maximum segment size
Date: Mon, 28 Sep 2026 09:58:53 -0300 [thread overview]
Message-ID: <20260928125853.GG163130@ziepe.ca> (raw)
In-Reply-To: <ea7da508-131e-4146-a737-5e8778866e03@amd.com>
On Mon, Sep 28, 2026 at 10:27:32AM +0200, Christian König wrote:
> In general I think that the sg_alloc_table_from_pages_segment()
> approach is because of the broken design of the old DMA API.
The scatterlist and the DMA API use of it is very specialized to serve
the needs of the storage stack without performance cost. Segmentation
is intended to make the sgl entries map 1:1 to HW entries so the block
layer can schedule correctly.
Nothing else needs something like this but still has to tip toe around
these rules. It makes it more complicated to map and then in some
cases you have to undo it when programming HW :\
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Jason
prev parent reply other threads:[~2026-09-28 12:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-26 7:12 Karl Mehltretter
2026-09-28 8:27 ` Christian König
2026-09-28 12:58 ` Jason Gunthorpe [this message]
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