zio-gpio: add an input cset

New input cset, at most 8 gpio pins in 1-byte-per-sample.
(Unlikely the previous one, this has been completed and tested)

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>
Acked-by: Federico Vaga <federico.vaga@gmail.com>

drivers/zio-gpio.c

@@ -22,11 +22,20 @@
 #include <linux/zio-buffer.h>
 
 #define ZGPIO_NOUT 8
+#define ZGPIO_NIN 8
 
+/* Output and input bits are selected at load time */
 static int zgp_out[ZGPIO_NOUT];
 static int zgp_nout;
 module_param_array_named(out, zgp_out, int, &zgp_nout, 0444);
+static int zgp_in[ZGPIO_NIN];
+static int zgp_nin;
+module_param_array_named(in, zgp_in, int, &zgp_nin, 0444);
 
+ZIO_PARAM_TRIGGER(zgp_trigger);
+ZIO_PARAM_BUFFER(zgp_buffer);
+
+/* This outputs a cset, currently made up of one channel only */
 static int zgp_output(struct zio_cset *cset)
 {
 	struct zio_channel *chan;
@@ -35,22 +44,48 @@ static int zgp_output(struct zio_cset *cset)
 	uint8_t datum;
 	int i;
 
-	/* we currently have one channel only, but who cares */
 	cset_for_each(cset, chan) {
 		block = chan->active_block;
 		if (!block)
 			continue;
 		ctrl = zio_get_ctrl(block);
-		/* FIXME: should use ssize */
-		datum = ((unsigned char *)block->data)[ctrl->nsamples - 1];
+		/* use last sample, as previous ones would be overwritten */
+		i = ctrl->ssize * ctrl->nsamples;
+		datum = ((unsigned char *)block->data)[i - 1];
 		for (i = 0; i < zgp_nout; i++)
 			gpio_set_value(zgp_out[i], datum & (1 << i));
 	}
 	return 1; /* done */
 }
 
+/* Similarly, this inputs a cset. Again, currently one channel only */
+static int zgp_input(struct zio_cset *cset)
+{
+	struct zio_channel *chan;
+	struct zio_block *block;
+	struct zio_control *ctrl;
+	uint8_t datum;
+	int i, j;
+
+	cset_for_each(cset, chan) {
+		block = chan->active_block;
+		if (!block)
+			continue;
+		ctrl = zio_get_ctrl(block);
+		/* fill the whole block */
+		for (j = 0; j < ctrl->nsamples; j++) {
+			datum = 0;
+			for (i = 0; i < zgp_nin; i++)
+				datum |= gpio_get_value(zgp_in[i]) << i;
+			((unsigned char *)block->data)[j] = datum;
+		}
+	}
+	return 1; /* done */
+}
+
 static struct zio_device_operations zgp_d_op = {
 	.output_cset =		zgp_output,
+	.input_cset =		zgp_input,
 };
 
 static struct zio_cset zgp_cset[] = {
@@ -59,6 +94,11 @@ static struct zio_cset zgp_cset[] = {
 		.ssize =	1,
 		.flags =	ZIO_DIR_OUTPUT | ZCSET_TYPE_ANALOG,
 	},
+	{
+		.n_chan =	1,
+		.ssize =	1,
+		.flags =	ZIO_DIR_INPUT | ZCSET_TYPE_ANALOG,
+	},
 };
 static struct zio_device zgp_dev = {
 	.owner =		THIS_MODULE,
@@ -72,6 +112,10 @@ static int __init zgp_init(void)
 {
 	int i, err;
 
+	/* The above code assumes we have one one-byte sized data */
+	BUILD_BUG_ON(ZGPIO_NOUT > 8);
+	BUILD_BUG_ON(ZGPIO_NIN > 8);
+
 	if (zgp_nout == 0) {
 		pr_err(KBUILD_MODNAME ": please pass out= gpio list\n");
 		return -ENODEV;
@@ -86,17 +130,37 @@ static int __init zgp_init(void)
 		}
 	}
 
+	for (i = 0; i < zgp_nin; i++) {
+		err = gpio_request(zgp_in[i], "zio-gpio-in");
+		if (err) {
+			pr_err(KBUILD_MODNAME ": can't request gpio %i\n",
+			       zgp_in[i]);
+			goto out_input;
+		}
+	}
+
+	if (zgp_trigger)
+		zgp_dev.preferred_trigger = zgp_trigger;
+	if (zgp_buffer)
+		zgp_dev.preferred_buffer = zgp_buffer;
 	err = zio_register_dev(&zgp_dev, "gpio");
 	if (err) {
 		pr_err(KBUILD_MODNAME ": can't register zio driver "
 		       "(error %i)\n", err);
-		goto out;
+		goto out_input;
 	}
 
 	for (i = 0; i < zgp_nout; i++)
 		gpio_direction_output(zgp_out[i], 0);
+	for (i = 0; i < zgp_nin; i++)
+		gpio_direction_input(zgp_in[i]);
 	return 0;
 
+out_input:
+	/* i is one more than the last registered gpio */
+	for (i--; i >= 0; i--)
+		gpio_free(zgp_in[i]);
+	i = zgp_nout;
 out:
 	/* i is one more than the last registered gpio */
 	for (i--; i >= 0; i--)
@@ -110,6 +174,8 @@ static void __exit zgp_exit(void)
 	zio_unregister_dev(&zgp_dev);
 	for (i = 0; i < zgp_nout; i++)
 		gpio_free(zgp_out[i]);
+	for (i = 0; i < zgp_nin; i++)
+		gpio_free(zgp_in[i]);
 }
 
 module_init(zgp_init);