Messages in this thread | | | Date | Sat, 10 Jun 2023 01:43:39 +0800 | Subject | Re: [Intel-gfx] [PATCH v3 4/4] PCI/VGA: introduce is_boot_device function callback to vga_client_register | From | Sui Jingfeng <> |
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On 2023/6/10 00:48, Bjorn Helgaas wrote: > On Fri, Jun 09, 2023 at 10:27:39AM +0800, Sui Jingfeng wrote: >> On 2023/6/9 03:19, Bjorn Helgaas wrote: >>> On Thu, Jun 08, 2023 at 07:43:22PM +0800, Sui Jingfeng wrote: >>>> From: Sui Jingfeng <suijingfeng@loongson.cn> >>>> >>>> The vga_is_firmware_default() function is arch-dependent, which doesn't >>>> sound right. At least, it also works on the Mips and LoongArch platforms. >>>> Tested with the drm/amdgpu and drm/radeon drivers. However, it's difficult >>>> to enumerate all arch-driver combinations. I'm wrong if there is only one >>>> exception. >>>> >>>> With the observation that device drivers typically have better knowledge >>>> about which PCI bar contains the firmware framebuffer, which could avoid >>>> the need to iterate all of the PCI BARs. >>>> >>>> But as a PCI function at pci/vgaarb.c, vga_is_firmware_default() is >>>> probably not suitable to make such an optimization for a specific device. >>>> >>>> There are PCI display controllers that don't have a dedicated VRAM bar, >>>> this function will lose its effectiveness in such a case. Luckily, the >>>> device driver can provide an accurate workaround. >>>> >>>> Therefore, this patch introduces a callback that allows the device driver >>>> to tell the VGAARB if the device is the default boot device. This patch >>>> only intends to introduce the mechanism, while the implementation is left >>>> to the device driver authors. Also honor the comment: "Clients have two >>>> callback mechanisms they can use" >>> s/bar/BAR/ (several) >>> >>> Nothing here uses the callback. I don't want to merge this until we >>> have a user. >> This is chicken and egg question. >> >> If you could help get this merge first, I will show you the first user. >> >>> I'm not sure why the device driver should know whether its device is >>> the default boot device. >> It's not that the device driver should know, >> >> but it's about that the device driver has the right to override. >> >> Device driver may have better approach to identify the default boot >> device. > The way we usually handle this is to include the new callback in the > same series as the first user of it. That has two benefits: > (1) everybody can review the whole picture and possibly suggest > different approaches, and (2) when we merge the infrastructure, > we also merge a user of it at the same time, so the whole thing can be > tested and we don't end up with unused code.
OK, acceptable
I will try to prepare the user code of this callback and respin the patch.
I may resend it with another patch set in the future, this series already drop it,
see v5[1]
[1] https://patchwork.freedesktop.org/series/119134/
> Bjorn
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