linux-kernel - [PATCH v4 4/7] pwm: cros-ec: Accept more error codes from cros_ec_cmd_xfer

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Date:   Thu,  6 Aug 2020 08:33:05 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Benson Leung <bleung@...omium.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Lee Jones <lee.jones@...aro.org>,
        Gwendal Grignou <gwendal@...omium.org>,
        Brian Norris <briannorris@...omium.org>,
        Yu-Hsuan Hsu <yuhsuan@...omium.org>,
        Prashant Malani <pmalani@...omium.org>,
        linux-iio@...r.kernel.org, linux-input@...r.kernel.org,
        linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH v4 4/7] pwm: cros-ec: Accept more error codes from cros_ec_cmd_xfer_status

Since commit c5cd2b47b203 ("platform/chrome: cros_ec_proto: Report command
not supported") we can no longer assume that cros_ec_cmd_xfer_status()
reports -EPROTO for all errors returned by the EC itself. A follow-up
patch will change cros_ec_cmd_xfer_status() to report additional errors
reported by the EC as distinguished Linux error codes.

Handle this change by no longer assuming that only -EPROTO is used
to report all errors returned by the EC itself. Instead, support both
the old and the new error codes.

Add a comment describing cros_ec_num_pwms() to explain its functionality.

Cc: Gwendal Grignou <gwendal@...omium.org>
Cc: Yu-Hsuan Hsu <yuhsuan@...omium.org>
Cc: Prashant Malani <pmalani@...omium.org>
Cc: Brian Norris <briannorris@...omium.org>
Acked-by: Thierry Reding <thierry.reding@...il.com>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
v4: Added comments describing cros_ec_num_pwms() in more detail
    Added Thierry's Acked-by: tag
v3: Added patch

 drivers/pwm/pwm-cros-ec.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/drivers/pwm/pwm-cros-ec.c b/drivers/pwm/pwm-cros-ec.c
index 09c08dee099e..94d3dff9b0e5 100644
--- a/drivers/pwm/pwm-cros-ec.c
+++ b/drivers/pwm/pwm-cros-ec.c
@@ -204,6 +204,11 @@ static const struct pwm_ops cros_ec_pwm_ops = {
 	.owner		= THIS_MODULE,
 };
 
+/*
+ * Determine the number of supported PWMs. The EC does not return the number
+ * of PWMs it supports directly, so we have to read the pwm duty cycle for
+ * subsequent channels until we get an error.
+ */
 static int cros_ec_num_pwms(struct cros_ec_device *ec)
 {
 	int i, ret;
@@ -213,20 +218,30 @@ static int cros_ec_num_pwms(struct cros_ec_device *ec)
 		u32 result = 0;
 
 		ret = __cros_ec_pwm_get_duty(ec, i, &result);
-		/* We want to parse EC protocol errors */
-		if (ret < 0 && !(ret == -EPROTO && result))
-			return ret;
-
 		/*
 		 * We look for SUCCESS, INVALID_COMMAND, or INVALID_PARAM
 		 * responses; everything else is treated as an error.
+		 * The EC error codes either map to -EOPNOTSUPP / -EINVAL,
+		 * or -EPROTO is returned and the EC error is in the result
+		 * field. Check for both.
 		 */
-		if (result == EC_RES_INVALID_COMMAND)
+		switch (ret) {
+		case -EOPNOTSUPP:	/* invalid command */
 			return -ENODEV;
-		else if (result == EC_RES_INVALID_PARAM)
+		case -EINVAL:		/* invalid parameter */
 			return i;
-		else if (result)
+		case -EPROTO:
+			/* Old or new error return code: Handle both */
+			if (result == EC_RES_INVALID_COMMAND)
+				return -ENODEV;
+			else if (result == EC_RES_INVALID_PARAM)
+				return i;
 			return -EPROTO;
+		default:
+			if (ret < 0)
+				return ret;
+			break;
+		}
 	}
 
 	return U8_MAX;
-- 
2.17.1