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From: Arnd Bergmann <arnd@arndb.de>
To: Michael Kelley <mikelley@microsoft.com>
Cc: Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	gregkh <gregkh@linuxfoundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	linux-efi <linux-efi@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	"olaf@aepfle.de" <olaf@aepfle.de>,
	Andy Whitcroft <apw@canonical.com>,
	vkuznets <vkuznets@redhat.com>, Jason Wang <jasowang@redhat.com>,
	"marcelo.cerri@canonical.com" <marcelo.cerri@canonical.com>,
	KY Srinivasan <kys@microsoft.com>,
	Sunil Muthuswamy <sunilmut@microsoft.com>,
	Boqun Feng <boqun.feng@gmail.com>
Subject: Re: [PATCH v6 09/10] arm64: efi: Export screen_info
Date: Wed, 18 Mar 2020 10:26:52 +0100
Message-ID: <CAK8P3a1YCtc3LJ-_3iT90_Srehb96gLHvTXsbJ0wT6NFYCG=TQ@mail.gmail.com> (raw)
In-Reply-To: <MW2PR2101MB10524254D2FE3EFC72329465D7F70@MW2PR2101MB1052.namprd21.prod.outlook.com>

On Wed, Mar 18, 2020 at 1:18 AM Michael Kelley <mikelley@microsoft.com> wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> > On Sat, Mar 14, 2020 at 4:36 PM Michael Kelley <mikelley@microsoft.com> wrote:
> > >
> > > The Hyper-V frame buffer driver may be built as a module, and
> > > it needs access to screen_info. So export screen_info.
> > >
> > > Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> >
> > Is there any chance of using a more modern KMS based driver for the screen
> > than the old fbdev subsystem? I had hoped to one day completely remove
> > support for the old CONFIG_VIDEO_FBDEV and screen_info from modern
> > architectures.
> >
>
> The current hyperv_fb.c driver is all we have today for the synthetic Hyper-V
> frame buffer device.  That driver builds and runs on both ARM64 and x86.
>
> I'm not knowledgeable about video/graphics drivers, but when you
> say "a more modern KMS based driver", are you meaning one based on
> DRM & KMS?  Does DRM make sense for a "dumb" frame buffer device?
> Are there any drivers that would be a good pattern to look at?

It used to be a lot harder to write a DRM driver compared to an fbdev
driver, but this has changed to the opposite over the years.

A fairly minimal example would be drivers/gpu/drm/pl111/pl111_drv.c
or anything in drivers/gpu/drm/tiny/, but you may want to look at the
other hypervisor platforms first, i.e drivers/gpu/drm/virtio/virtgpu_drv.c,
drivers/gpu/drm/vmwgfx/vmwgfx_drv.c, drivers/gpu/drm/xen/xen_drm_front.c,
drivers/gpu/drm/qxl/qxl_drv.c, and drivers/gpu/drm/bochs/bochs_drv.c.

       Arnd

  reply index

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-14 15:35 [PATCH v6 00/10] Subject: Enable Linux guests on Hyper-V on ARM64 Michael Kelley
2020-03-14 15:35 ` [PATCH v6 01/10] arm64: hyperv: Add core Hyper-V include files Michael Kelley
2020-03-15 17:31   ` Marc Zyngier
2020-03-18  0:10     ` Michael Kelley
2020-03-16  8:47   ` Arnd Bergmann
2020-03-18  0:12     ` Michael Kelley
2020-03-18 10:10       ` Arnd Bergmann
2020-03-19 21:31         ` Michael Kelley
2020-03-20 16:38           ` Arnd Bergmann
2020-03-14 15:35 ` [PATCH v6 02/10] arm/arm64: smccc-1.1: Add vendor specific owner definition Michael Kelley
2020-03-14 15:35 ` [PATCH v6 03/10] arm64: hyperv: Add hypercall and register access functions Michael Kelley
2020-03-14 15:35 ` [PATCH v6 04/10] arm64: hyperv: Add memory alloc/free functions for Hyper-V size pages Michael Kelley
2020-03-16  8:22   ` Arnd Bergmann
2020-03-16  8:30     ` gregkh
2020-03-16  8:30     ` Marc Zyngier
2020-03-16  8:32       ` Arnd Bergmann
2020-03-18  0:15         ` Michael Kelley
2020-03-18  9:57           ` Arnd Bergmann
2020-03-19 21:43             ` Michael Kelley
2020-03-20 16:28               ` Arnd Bergmann
2020-03-20 17:22                 ` Michael Kelley
2020-03-14 15:35 ` [PATCH v6 05/10] arm64: hyperv: Add interrupt handlers for VMbus and stimer Michael Kelley
2020-03-16  8:25   ` Arnd Bergmann
2020-03-18  0:16     ` Michael Kelley
2020-03-18  9:52       ` Arnd Bergmann
2020-03-14 15:35 ` [PATCH v6 06/10] arm64: hyperv: Add kexec and panic handlers Michael Kelley
2020-03-15 18:15   ` Marc Zyngier
2020-03-18  0:17     ` Michael Kelley
2020-03-14 15:35 ` [PATCH v6 07/10] arm64: hyperv: Initialize hypervisor on boot Michael Kelley
2020-03-16  8:29   ` Arnd Bergmann
2020-03-18  0:17     ` Michael Kelley
2020-03-18  9:44       ` Arnd Bergmann
2020-03-14 15:35 ` [PATCH v6 08/10] Drivers: hv: vmbus: Add hooks for per-CPU IRQ Michael Kelley
2020-03-14 15:35 ` [PATCH v6 09/10] arm64: efi: Export screen_info Michael Kelley
2020-03-16  8:20   ` Arnd Bergmann
2020-03-18  0:18     ` Michael Kelley
2020-03-18  9:26       ` Arnd Bergmann [this message]
2020-03-19 21:46         ` Michael Kelley
2020-05-13 14:26           ` Nikhil Mahale
2020-05-18  4:25             ` Nikhil Mahale
2020-05-18 12:51               ` Ard Biesheuvel
2020-05-22 11:14                 ` Nikhil Mahale
2020-05-22 11:32                   ` Ard Biesheuvel
2020-03-14 15:35 ` [PATCH v6 10/10] Drivers: hv: Enable Hyper-V code to be built on ARM64 Michael Kelley
     [not found] ` <20200318031130.5476-1-hdanton@sina.com>
2020-03-19 21:04   ` [PATCH v6 03/10] arm64: hyperv: Add hypercall and register access functions Michael Kelley

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