Re: [PATCH 3/5] drivers/thunderbolt: Don't make DROM read success compulsory

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Hi Mario,

On Wed, Mar 02, 2022 at 04:07:07PM -0600, Mario Limonciello wrote:
> The USB4 specification doesn't make any requirements that reading
> a device router's DROM is needed for the operation of the device.
> 
> On page 207 of the USB4 1.0 spec it does mention that a CM may use
> the DROM to make decision though:
> ```
> After enumerating a Router, the Connection Manager may read the
> contents of the Router’s DROM. If, after reading the contents of
> DROM, the Connection Manager decides that it does not want the
> Router in its Domain...
> ```

You don't need to quote the spec for Thunderbolt patches. I can read,
and it's not like it is going to change anyway ;-)

> Other connection manager solutions don't necessarily read it or gate
> the usability of the device on whether it was read.

Indeed.

> So make failures when reading the DROM show warnings but not
> fail the initialization of the switch.
> 
> Link: https://www.usb.org/sites/default/files/USB4%20Specification%2020211116.zip

Also no need to "link" the spec. I know where the spec can be
downloaded.

Ditto for all patches.

> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
>  drivers/thunderbolt/switch.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
> index 294518af4ee4..ac87e8b50e52 100644
> --- a/drivers/thunderbolt/switch.c
> +++ b/drivers/thunderbolt/switch.c
> @@ -2784,10 +2784,8 @@ int tb_switch_add(struct tb_switch *sw)
>  
>  		/* read drom */
>  		ret = tb_drom_read(sw);
> -		if (ret) {
> -			dev_err(&sw->dev, "reading DROM failed\n");
> -			return ret;
> -		}
> +		if (ret)
> +			dev_warn(&sw->dev, "reading DROM failed: %d\n", ret);
>  		tb_sw_dbg(sw, "uid: %#llx\n", sw->uid);
>  
>  		tb_check_quirks(sw);
> -- 
> 2.34.1