[U-Boot] [PATCH V2 2/2] pci: Update documentation to make 'compatible' string optional

[Simon Glass]

Hi Marek,

On 24 August 2018 at 12:27, Marek Vasut <marek.vasut at gmail.com> wrote:
> Reword the documentation to make it clear the compatible string is now
> optional, yet still matching on it takes precedence over PCI IDs and
> PCI classes.
>
> Signed-off-by: Marek Vasut <marek.vasut+renesas at gmail.com>
> Cc: Simon Glass <sjg at chromium.org>
> Cc: Tom Rini <trini at konsulko.com>
> ---
> V2: New patch
> ---
>  doc/driver-model/pci-info.txt | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/doc/driver-model/pci-info.txt b/doc/driver-model/pci-info.txt
> index e1701d1fbc..14364c5c75 100644
> --- a/doc/driver-model/pci-info.txt
> +++ b/doc/driver-model/pci-info.txt
> @@ -34,11 +34,15 @@ under that bus.
>  Note that this is all done on a lazy basis, as needed, so until something is
>  touched on PCI (eg: a call to pci_find_devices()) it will not be probed.
>
> -PCI devices can appear in the flattened device tree. If they do this serves to
> -specify the driver to use for the device. In this case they will be bound at
> -first. Each PCI device node must have a compatible string list as well as a
> -<reg> property, as defined by the IEEE Std 1275-1994 PCI bus binding document
> -v2.1. Note we must describe PCI devices with the same bus hierarchy as the
> +PCI devices can appear in the flattened device tree. If they do, their node
> +often contains extra information which cannot be derived from the PCI IDs or
> +PCI class of the device. Each PCI device node must have a <reg> property, as
> +defined by the IEEE Std 1275-1994 PCI bus binding document v2.1. Compatible
> +string list is optional and generally not needed, since PCI is discoverable
> +bus, albeit there are justified exceptions. If the compatible string is
> +present, matching on it takes precedence over PCI IDs and PCI classes.
> +
> +Note we must describe PCI devices with the same bus hierarchy as the
>  hardware, otherwise driver model cannot detect the correct parent/children
>  relationship during PCI bus enumeration thus PCI devices won't be bound to
>  their drivers accordingly. A working example like below:
> --
> 2.16.2
>

Are we really saying that compatible strings are 'generally not needed'?

device tree pci supplement 2.1 talks about some new formats for the
compatible string, but doesn't say it is not needed. I much prefer a
compatible string since it is easy to find the driver in the source
code.

Can way say that a compatible string is preferred, but in extremis you
can avoid it by...


Regards,
Simon