linux-kernel - Re: [RFC 26/32] drm: handle HAS

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Date:   Mon, 3 Jan 2022 07:11:27 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     Niklas Schnelle <schnelle@...ux.ibm.com>
Cc:     Arnd Bergmann <arnd@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        John Garry <john.garry@...wei.com>,
        Nick Hu <nickhu@...estech.com>,
        Greentime Hu <green.hu@...il.com>,
        Vincent Chen <deanbo422@...il.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>,
        Dave Airlie <airlied@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-csky@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        spice-devel@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Subject: Re: [RFC 26/32] drm: handle HAS_IOPORT dependencies

On Mon, Dec 27, 2021 at 05:43:11PM +0100, Niklas Schnelle wrote:
> In a future patch HAS_IOPORT=n will result in inb()/outb() and friends
> not being declared. We thus need to add HAS_IOPORT as dependency for
> those drivers using them. There is also a direct and hard coded use in
> cirrus.c which according to the comment is only necessary during resume.
> Let's just skip this as for example s390 which doesn't have I/O port
> support also doesen't support suspend/resume.

>  config DRM_BOCHS
>  	tristate "DRM Support for bochs dispi vga interface (qemu stdvga)"
>  	depends on DRM && PCI && MMU
> +	depends on HAS_IOPORT
>  	select DRM_KMS_HELPER
>  	select DRM_VRAM_HELPER
>  	select DRM_TTM

On devices with an mmio bar the driver works just fine without inb/outb,
see bochs->mmio checks in bochs.c

take care,
  Gerd