iopoll: Generalize read_poll_timeout() into poll_timeout_us()

While read_poll_timeout() & co. were originally introduced just
for simple I/O usage scenarios they have since been generalized to
be useful in more cases.

However the interface is very cumbersome to use in the general case.
Attempt to make it more flexible by combining the 'op', 'var' and
'args' parameter into just a single 'op' that the caller can fully
specify.

For example i915 has one case where one might currently
have to write something like:
	ret = read_poll_timeout(drm_dp_dpcd_read_byte, err,
				err || (status & mask),
				0 * 1000, 200 * 1000, false,
				aux, DP_FEC_STATUS, &status);
which is practically illegible, but with the adjusted macro
we do:
	ret = poll_timeout_us(err = drm_dp_dpcd_read_byte(aux, DP_FEC_STATUS, &status),
			      err || (status & mask),
			      0 * 1000, 200 * 1000, false);
which much easier to understand.

One could even combine the 'op' and 'cond'  parameters into
one, but that might make the caller a bit too unwieldly with
assignments and checks being done on the same statement.

This makes poll_timeout_us() closer to the i915 __wait_for()
macro, with the main difference being that __wait_for() uses
expenential backoff as opposed to the fixed polling interval
used by poll_timeout_us(). Eventually we might be able to switch
(at least most of) i915 to use poll_timeout_us().

v2: Fix typos (Jani)
    Fix delay_us docs for poll_timeout_us_atomic() (Jani)

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Dibin Moolakadan Subrahmanian <dibin.moolakadan.subrahmanian@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: David Laight <david.laight.linux@gmail.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Matt Wagantall <mattw@codeaurora.org>
Cc: Dejin Zheng <zhengdejin5@gmail.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: intel-xe@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Simona Vetter <simona.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://lore.kernel.org/r/20250826121859.15497-1-ville.syrjala@linux.intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

0 files changed, 0 insertions, 0 deletions