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Message-ID: <Yyhs7CW1iZKGfKab@hovoldconsulting.com>
Date: Mon, 19 Sep 2022 15:21:48 +0200
From: Johan Hovold <johan@...nel.org>
To: Jiasheng Jiang <jiasheng@...as.ac.cn>
Cc: gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] USB: serial: ftdi_sio: Convert to use dev_groups
On Wed, Sep 14, 2022 at 03:13:34PM +0800, Jiasheng Jiang wrote:
> The driver core supports the ability to handle the creation and removal
> of device-specific sysfs files in a race-free manner.
> Moreover, it can
> guarantee the success of creation.
I don't believe this is true, driver core just handles the errors.
> Therefore, it should be better to
> convert to use dev_groups.
> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
> ---
> Changelog:
>
> v4 -> v5:
>
> 1. Use a forward declaration for ftdi_sio_groups.
> 2. Correct ftdi_sio_attr_is_visible() implementation.
>
> v3 -> v4:
>
> 1. Move the code and remove the pre-definitions.
>
> v2 -> v3:
>
> 1. Add is_visible to filter the unneeded files.
>
> v1 -> v2:
>
> 1. Change the title.
> 2. Switch to use an attribute group.
> ---
> drivers/usb/serial/ftdi_sio.c | 60 +++++++++++++++++------------------
> 1 file changed, 29 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
> index d5a3986dfee7..660181064cda 100644
> --- a/drivers/usb/serial/ftdi_sio.c
> +++ b/drivers/usb/serial/ftdi_sio.c
> @@ -1108,10 +1108,13 @@ static u32 ftdi_232bm_baud_to_divisor(int baud);
> static u32 ftdi_2232h_baud_base_to_divisor(int baud, int base);
> static u32 ftdi_2232h_baud_to_divisor(int baud);
>
> +extern const struct attribute_group *ftdi_sio_groups[];
Why did you use extern here? Should be static.
> +
> static struct usb_serial_driver ftdi_sio_device = {
> .driver = {
> .owner = THIS_MODULE,
> .name = "ftdi_sio",
> + .dev_groups = ftdi_sio_groups,
> },
> .description = "FTDI USB Serial Device",
> .id_table = id_table_combined,
> @@ -1729,38 +1732,19 @@ static ssize_t event_char_store(struct device *dev,
> }
> static DEVICE_ATTR_WO(event_char);
>
> -static int create_sysfs_attrs(struct usb_serial_port *port)
> +static umode_t ftdi_sio_attr_is_visible(struct kobject *kobj,
> + struct attribute *attr, int idx)
I'd drop the "sio" infix from all of these new symbols and just call
this one ftdi_is_visible().
> {
> + struct device *dev = kobj_to_dev(kobj);
> + struct usb_serial_port *port = container_of(dev, struct usb_serial_port, dev);
> struct ftdi_private *priv = usb_get_serial_port_data(port);
> - int retval = 0;
> + umode_t mode = attr->mode;
>
> /* XXX I've no idea if the original SIO supports the event_char
> * sysfs parameter, so I'm playing it safe. */
> if (priv->chip_type != SIO) {
> - dev_dbg(&port->dev, "sysfs attributes for %s\n", ftdi_chip_name[priv->chip_type]);
> - retval = device_create_file(&port->dev, &dev_attr_event_char);
> - if ((!retval) &&
> - (priv->chip_type == FT232BM ||
> - priv->chip_type == FT2232C ||
> - priv->chip_type == FT232RL ||
> - priv->chip_type == FT2232H ||
> - priv->chip_type == FT4232H ||
> - priv->chip_type == FT232H ||
> - priv->chip_type == FTX)) {
> - retval = device_create_file(&port->dev,
> - &dev_attr_latency_timer);
> - }
> - }
> - return retval;
> -}
> -
> -static void remove_sysfs_attrs(struct usb_serial_port *port)
> -{
> - struct ftdi_private *priv = usb_get_serial_port_data(port);
> -
> - /* XXX see create_sysfs_attrs */
> - if (priv->chip_type != SIO) {
> - device_remove_file(&port->dev, &dev_attr_event_char);
> + if (attr == &dev_attr_event_char.attr)
> + return mode;
> if (priv->chip_type == FT232BM ||
> priv->chip_type == FT2232C ||
> priv->chip_type == FT232RL ||
> @@ -1768,12 +1752,29 @@ static void remove_sysfs_attrs(struct usb_serial_port *port)
> priv->chip_type == FT4232H ||
> priv->chip_type == FT232H ||
> priv->chip_type == FTX) {
> - device_remove_file(&port->dev, &dev_attr_latency_timer);
> + if (attr == &dev_attr_latency_timer.attr)
> + return mode;
> }
> }
> -
> + return 0;
> }
>
> +static struct attribute *ftdi_sio_attrs[] = {
> + &dev_attr_event_char.attr,
> + &dev_attr_latency_timer.attr,
> + NULL,
nit: no need for comma after NULL.
> +};
> +
> +static const struct attribute_group ftdi_sio_group = {
> + .attrs = ftdi_sio_attrs,
> + .is_visible = ftdi_sio_attr_is_visible,
> +};
> +
> +const struct attribute_group *ftdi_sio_groups[] = {
Missing static.
> + &ftdi_sio_group,
> + NULL
> +};
> +
> #ifdef CONFIG_GPIOLIB
>
> static int ftdi_set_bitmode(struct usb_serial_port *port, u8 mode)
> @@ -2251,7 +2252,6 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
> if (read_latency_timer(port) < 0)
> priv->latency = 16;
> write_latency_timer(port);
> - create_sysfs_attrs(port);
>
> result = ftdi_gpio_init(port);
> if (result < 0) {
> @@ -2377,8 +2377,6 @@ static void ftdi_sio_port_remove(struct usb_serial_port *port)
>
> ftdi_gpio_remove(port);
>
> - remove_sysfs_attrs(port);
> -
> kfree(priv);
> }
But in general this looks good now.
There has been some recent changes to how this driver handles device
types so I rebased this patch on top, fixed up the above and amended the
commit message. The result is here:
https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial.git/commit/?h=usb-next&id=0f6632e2e8beb6a1e0895c1309dd0b84b805c202
Thanks.
Johan
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