ptp: Make max_phase_adjustment sysfs device attribute invisible when not supported

The .adjphase operation is an operation that is implemented only by certain
PHCs. The sysfs device attribute node for querying the maximum phase
adjustment supported should not be exposed on devices that do not support
.adjphase.

Fixes: c3b60ab ("ptp: Add .getmaxphase callback to ptp_clock_info")
Signed-off-by: Rahul Rameshbabu <[email protected]>
Reported-by: Nathan Chancellor <[email protected]>
Reported-by: Naresh Kamboju <[email protected]>
Reported-by: Linux Kernel Functional Testing <[email protected]>
Link: https://lore.kernel.org/netdev/[email protected]/
Link: https://lore.kernel.org/all/CA+G9fYtKCZeAUTtwe69iK8Xcz1mOKQzwcy49wd+imZrfj6ifXA@mail.gmail.com/
Tested-by: Nathan Chancellor <[email protected]>
Reviewed-by: Andrew Lunn <[email protected]>
Acked-by: Richard Cochran <[email protected]>
Reviewed-by: Petr Vorel <[email protected]>
Message-ID: <[email protected]>
Signed-off-by: Jakub Kicinski <[email protected]>

Orabug: 35622106

(cherry picked from commit 2c5d234)
cherry-pick-repo=kernel/git/torvalds/linux.git
unmodified-from-upstream: 2c5d234

Signed-off-by: Mikhael Goikhman <[email protected]>
Signed-off-by: Qing Huang <[email protected]>
Reviewed-by: Devesh Sharma <[email protected]>
Signed-off-by: Brian Maly <[email protected]>

Author: Binary-Eater

drivers/ptp/ptp_sysfs.c

@@ -356,6 +356,9 @@ static umode_t ptp_is_attribute_visible(struct kobject *kobj,
 		   attr == &dev_attr_max_vclocks.attr) {
 		if (ptp->is_virtual_clock)
 			mode = 0;
+	} else if (attr == &dev_attr_max_phase_adjustment.attr) {
+		if (!info->adjphase || !info->getmaxphase)
+			mode = 0;
 	}
 
 	return mode;