Re: [PATCH 2/9] thunderblot: Don't pass a bitfield to FIELD_GET

On Wed, 10 Dec 2025 06:56:17 +0100
Mika Westerberg [off-list ref] wrote:

$subject has typo: thunderblot -> thunderbolt ;-)

On Tue, Dec 09, 2025 at 10:03:06AM +0000, david.laight.linux@gmail.com wrote:

quoted

From: David Laight <redacted>

FIELD_GET needs to use __auto_type to get the value of the 'reg'
parameter, this can't be used with bifields.

FIELD_GET also want to verify the size of 'reg' so can't add zero
to force the type to int.

So add a zero here.

Signed-off-by: David Laight <redacted>
---
 drivers/thunderbolt/tb.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index e96474f17067..7ca2b5a0f01e 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h

@@ -1307,7 +1307,7 @@ static inline struct tb_retimer *tb_to_retimer(struct device *dev)
  */
 static inline unsigned int usb4_switch_version(const struct tb_switch *sw)
 {
-	return FIELD_GET(USB4_VERSION_MAJOR_MASK, sw->config.thunderbolt_version);
+	return FIELD_GET(USB4_VERSION_MAJOR_MASK, sw->config.thunderbolt_version + 0);  

Can't this use a cast instead? If not then can you also add a comment here
because next someone will send a patch "fixing" the unnecessary addition.

A cast can do other (possibly incorrect) conversions, adding zero is never going
to so any 'damage' - even if it looks a bit odd.

Actually, I suspect the best thing here is to delete USB4_VERSION_MAJOR_MASK and
just do:
	/* The major version is in the top 3 bits */
	return sw->config.thunderbolt_version > 5;

The only other uses of thunderbolt_version are debug prints (in decimal).

	David

quoted

 }
 
 /**
-- 
2.39.5