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Date: Sun, 16 Aug 2020 16:40:01 +0200
From: Bartosz Golaszewski <bgolaszewski@...libre.com>
To: Kent Gibson <warthog618@...il.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
linux-gpio <linux-gpio@...r.kernel.org>,
Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v4 10/20] gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL
On Fri, Aug 14, 2020 at 5:04 AM Kent Gibson <warthog618@...il.com> wrote:
>
> Add support for GPIO_V2_LINE_SET_CONFIG_IOCTL, the uAPI v2
> line set config ioctl.
>
> Signed-off-by: Kent Gibson <warthog618@...il.com>
> ---
> drivers/gpio/gpiolib-cdev.c | 92 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 92 insertions(+)
>
> diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
> index 1d42a01f5414..04472c2b6678 100644
> --- a/drivers/gpio/gpiolib-cdev.c
> +++ b/drivers/gpio/gpiolib-cdev.c
> @@ -16,6 +16,7 @@
> #include <linux/kernel.h>
> #include <linux/kfifo.h>
> #include <linux/module.h>
> +#include <linux/mutex.h>
> #include <linux/pinctrl/consumer.h>
> #include <linux/poll.h>
> #include <linux/spinlock.h>
> @@ -418,6 +419,8 @@ struct edge_detector {
> * @seqno: the sequence number for edge events generated on all lines in
> * this line request. Note that this is not used when @num_descs is 1, as
> * the line_seqno is then the same and is cheaper to calculate.
> + * @config_mutex: mutex for serializing ioctl() calls to ensure consistency
> + * of configuration, particularly multi-step accesses to desc flags.
> * @edets: an array of edge detectors, of size @num_descs
> * @descs: the GPIO descriptors held by this line request, with @num_descs
> * elements.
> @@ -429,6 +432,7 @@ struct line {
> wait_queue_head_t wait;
> DECLARE_KFIFO_PTR(events, struct gpio_v2_line_event);
> atomic_t seqno;
> + struct mutex config_mutex;
> struct edge_detector *edets;
> struct gpio_desc *descs[];
> };
> @@ -703,6 +707,30 @@ static int gpio_v2_line_config_validate(struct gpio_v2_line_config *lc,
> return 0;
> }
>
> +static int gpio_v2_line_config_change_validate(struct line *line,
> + struct gpio_v2_line_config *lc)
> +{
> + int i;
> + u64 flags;
> + struct gpio_desc *desc;
> +
> + for (i = 0; i < line->num_descs; i++) {
> + desc = line->descs[i];
> + flags = gpio_v2_line_config_flags(lc, i);
> + /* disallow edge detection changes */
> + if (line->edets[i].flags != (flags & GPIO_V2_LINE_EDGE_FLAGS))
> + return -EINVAL;
> +
> + if (line->edets[i].flags) {
> + /* disallow polarity changes */
> + if (test_bit(FLAG_ACTIVE_LOW, &desc->flags) !=
> + ((flags & GPIO_V2_LINE_FLAG_ACTIVE_LOW) != 0))
> + return -EINVAL;
> + }
> + }
> + return 0;
> +}
> +
> static void gpio_v2_line_config_flags_to_desc_flags(u64 flags,
> unsigned long *flagsp)
> {
> @@ -783,6 +811,67 @@ static long line_get_values(struct line *line, void __user *ip)
> return 0;
> }
>
> +static long line_set_config_locked(struct line *line,
> + struct gpio_v2_line_config *lc)
I think that the general consensus in the kernel is to suffix
functions that need to be called with some lock taken outside them
with _unlocked (as in: the function is unlocked on its own).
Alternatively such routines are prefixed with __ (__line_set_config())
but I know Linus prefers the former.
Bart
> +{
> + struct gpio_desc *desc;
> + int i, ret;
> + u64 flags;
> +
> + ret = gpio_v2_line_config_change_validate(line, lc);
> + if (ret)
> + return ret;
> +
> + for (i = 0; i < line->num_descs; i++) {
> + desc = line->descs[i];
> + flags = gpio_v2_line_config_flags(lc, i);
> +
> + gpio_v2_line_config_flags_to_desc_flags(flags, &desc->flags);
> + /*
> + * Lines have to be requested explicitly for input
> + * or output, else the line will be treated "as is".
> + */
> + if (flags & GPIO_V2_LINE_FLAG_OUTPUT) {
> + int val = gpio_v2_line_config_output_value(lc, i);
> +
> + edge_detector_stop(&line->edets[i]);
> + ret = gpiod_direction_output(desc, val);
> + if (ret)
> + return ret;
> + } else if (flags & GPIO_V2_LINE_FLAG_INPUT) {
> + ret = gpiod_direction_input(desc);
> + if (ret)
> + return ret;
> + }
> +
> + blocking_notifier_call_chain(&desc->gdev->notifier,
> + GPIO_V2_LINE_CHANGED_CONFIG,
> + desc);
> + }
> + return 0;
> +}
> +
> +static long line_set_config(struct line *line, void __user *ip)
> +{
> + struct gpio_v2_line_config lc;
> + int ret;
> +
> + if (copy_from_user(&lc, ip, sizeof(lc)))
> + return -EFAULT;
> +
> + ret = gpio_v2_line_config_validate(&lc, line->num_descs);
> + if (ret)
> + return ret;
> +
> + mutex_lock(&line->config_mutex);
> +
> + ret = line_set_config_locked(line, &lc);
> +
> + mutex_unlock(&line->config_mutex);
> +
> + return ret;
> +}
> +
> static long line_ioctl(struct file *file, unsigned int cmd,
> unsigned long arg)
> {
> @@ -791,6 +880,8 @@ static long line_ioctl(struct file *file, unsigned int cmd,
>
> if (cmd == GPIO_V2_LINE_GET_VALUES_IOCTL)
> return line_get_values(line, ip);
> + else if (cmd == GPIO_V2_LINE_SET_CONFIG_IOCTL)
> + return line_set_config(line, ip);
>
> return -EINVAL;
> }
> @@ -964,6 +1055,7 @@ static int line_create(struct gpio_device *gdev, void __user *ip)
> }
> }
>
> + mutex_init(&line->config_mutex);
> init_waitqueue_head(&line->wait);
> if (has_edge_detection) {
> size = lr.event_buffer_size;
> --
> 2.28.0
>
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