Re: [PATCH 0/6] drm/bridge: Add a BPF-based MIPI-DSI panel driver

[Javier Martinez Canillas]

Maxime Ripard <mripard@xxxxxxxxxx> writes:

> On Mon, Sep 28, 2026 at 10:36:18PM +0200, Neil Armstrong wrote:
>> On 9/28/26 21:48, Benjamin Tissoires wrote:
>> > On Sep 28 2026, Neil Armstrong wrote:
>> > > On 9/28/26 19:24, Benjamin Tissoires wrote:
>> > > > On Sep 28 2026, Neil Armstrong wrote:
>> > > > > Hi,
>> > > > > 
>> > > > > On 9/28/26 18:22, Maxime Ripard wrote:
>> > > > > > Hi,
>> > > > > > 
>> > > > > > Panels in general, and MIPI-DSI panels in particular, are pretty
>> > > > > > difficult to support and require pretty much a panel driver for each
>> > > > > > panel produced. Most of them are pretty simple, and require an opaque
>> > > > > > initialization sequence that is usually poorly documented.
>> > > > > > 
>> > > > > > This creates a tension between OEMs and distros because OEMs will
>> > > > > > typically get a new panel to react to a sourcing issue during
>> > > > > > production, and thus need some swift turnaround between getting their
>> > > > > > new panel and it being operational in the OS. Distributions on the other
>> > > > > > hand can take years to ship a kernel with that new panel driver.
>> > > > > > 
>> > > > > > To solve this, I followed the example of HID-BPF and wrote a panel
>> > > > > > driver that will rely on BPF programs to perform the panel
>> > > > > > initialization. That way, we can ship the programs separately from the
>> > > > > > kernel, and with a different lifecycle. If this driver is accepted, the
>> > > > > > plan is to have a userspace component started by udev to identify and
>> > > > > > load the right BPF program for the panels found on the device.
>> > > > > 
>> > > > > This is kind of late for serious applications except if we manage to
>> > > > > solve the bootloader to Linux display engine transition.
>> > > > > 

Besides what Maxime already mentioned (that most general purpose Linux distributions
built the drivers as modules anyways), it doesn't have to be mutually exclusive.

A simple panel could be supported using this BPF-based driver and then a panel driver
added to the kernel, if is found that some applications need to have it built-in and
earlier in the boot path.

I don't see why this would be any different than HDI-BPF or other BPF-based infra,
such as sched_ext.

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat