HID: mcp2221: Add module parameter to enfoce GPIO mode

Add a module parameter to MCP2221 to enfor GPIO mode on the
general purpose pins GP0 thru GP3.

If I plug a device of this type into my machine, it will use the
GP0, GP1, GP2 and GP3 pins for IIO voltage readings by default
if CONFIG_IIO is set.

However there may be cases where IIO is available but we want to
use the GP0 thru GP3 lines for GPIO anyway.

Example use:

insmode hid-mcp2221.ko gpio_mode_enforce=1

Result in dmesg:
mcp2221 0003:04D8:00DD.0005: GPIO 0 not in gpio mode
mcp2221 0003:04D8:00DD.0005: GPIO 1 not in gpio mode
mcp2221 0003:04D8:00DD.0005: GPIO 2 not in gpio mode
mcp2221 0003:04D8:00DD.0005: GPIO 3 not in gpio mode
mcp2221 0003:04D8:00DD.0005: Set GPIO mode for gpio pin 0!
mcp2221 0003:04D8:00DD.0005: Set GPIO mode for gpio pin 1!
mcp2221 0003:04D8:00DD.0005: Set GPIO mode for gpio pin 2!
mcp2221 0003:04D8:00DD.0005: Set GPIO mode for gpio pin 3!

After this the gpiolib tools such as gpioset can be used to alter
the GPIO line values successfully.

Signed-off-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

1 files changed, 14 insertions, 4 deletions

diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
index 64dcedbcc0fc..5c643f3c8c97 100644
--- a/drivers/hid/hid-mcp2221.c
+++ b/drivers/hid/hid-mcp2221.c
@@ -19,8 +19,15 @@
 #include <linux/gpio/driver.h>
 #include <linux/iio/iio.h>
 #include <linux/minmax.h>
+#include <linux/moduleparam.h>
 #include "hid-ids.h"
 
+static bool gpio_mode_enforce;
+
+module_param(gpio_mode_enforce, bool, 0644);
+MODULE_PARM_DESC(gpio_mode_enforce,
+	 "Enfore GPIO mode for GP0 thru GP3 (default: false, will be used for IIO)");
+
 /* Commands codes in a raw output report */
 enum {
 	MCP2221_I2C_WR_DATA = 0x90,
@@ -648,7 +655,7 @@ static int mcp2221_check_gpio_pinfunc(struct mcp2221 *mcp)
 	int needgpiofix = 0;
 	int ret;
 
-	if (IS_ENABLED(CONFIG_IIO))
+	if (IS_ENABLED(CONFIG_IIO) && !gpio_mode_enforce)
 		return 0;
 
 	ret = mcp_gpio_read_sram(mcp);
@@ -1043,7 +1050,8 @@ static void mcp2221_remove(struct hid_device *hdev)
 #if IS_REACHABLE(CONFIG_IIO)
 	struct mcp2221 *mcp = hid_get_drvdata(hdev);
 
-	cancel_delayed_work_sync(&mcp->init_work);
+	if (!gpio_mode_enforce)
+		cancel_delayed_work_sync(&mcp->init_work);
 #endif
 }
 
@@ -1317,8 +1325,10 @@ static int mcp2221_probe(struct hid_device *hdev,
 #endif
 
 #if IS_REACHABLE(CONFIG_IIO)
-	INIT_DELAYED_WORK(&mcp->init_work, mcp_init_work);
-	schedule_delayed_work(&mcp->init_work, msecs_to_jiffies(100));
+	if (!gpio_mode_enforce) {
+		INIT_DELAYED_WORK(&mcp->init_work, mcp_init_work);
+		schedule_delayed_work(&mcp->init_work, msecs_to_jiffies(100));
+	}
 #endif
 
 	return 0;