Hi Am 17.11.23 um 10:34 schrieb Maxime Ripard:
On Mon, Oct 09, 2023 at 04:06:29PM +0200, Thomas Zimmermann wrote:DRM's format-conversion helpers require temporary memory. Pass the buffer from the caller to allow the caller to preallocate the buffer memory. The motivation for this patchset is the recent work on a DRM panic handler. [1] The panic handler requires format conversion to display an error to the screen. But allocating memory during a kernel panic is fragile. The changes in this patchset enable the DRM panic handler to preallocate buffer storage before the panic occurs. Patch 1 adds struct drm_format_conv_state, a simple interface to pass around the buffer storage. Patch 2 adds an instance of the struct to the shadow-plane state. Patch 3 moves the buffer's memory management from the format helpers into their callers within the DRM drivers. Most of the affected drivers use the state instance stored in their shadow- plane state. The shadow-plane code releases the buffer memory automatically. Patches 4 to 7 update three drivers to pre-allocate the format-conversion buffer in their plane's atomic_check function. The drivers thus detect OOM errors before the display update begins. Tested with simpledrm.So, I just discovered that you merged that series. You've complained before about "sneaking patches in", and while I was disagreeing with you then, this particular instance is definitely a strong case for it. You've merged it without telling anyone, and despite our ongoing conversation on the v4 that was active more recently than the v5. And that you never responded to. Awesome.
My apologies. From my point of view, that conversion had ended. I left the patch set for a while to wait for further comments or questions, but nothing happened. So I merged it.
Revert it if you cannot live with the changes. IIRC you found the reduced number of alloc/free cycles to be irrelevant. But even then, the patches allow us to move the allocation from atomic_update to atomic_check, thus detecting allocation failures early. That's an improvement to me.
Best regards Thomas
Maxime
-- 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)
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