linux-kernel - Re: [PATCH v2 27/35] media: em28xx: cx231xx: fix opencoded find_and_set

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Date:   Mon, 4 Dec 2023 09:39:59 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Yury Norov <yury.norov@...il.com>, linux-kernel@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org
Cc:     Jan Kara <jack@...e.cz>,
        Mirsad Todorovac <mirsad.todorovac@....unizg.hr>,
        Matthew Wilcox <willy@...radead.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Maxim Kuvyrkov <maxim.kuvyrkov@...aro.org>,
        Alexey Klimov <klimov.linux@...il.com>,
        Bart Van Assche <bvanassche@....org>,
        Sergey Shtylyov <s.shtylyov@....ru>
Subject: Re: [PATCH v2 27/35] media: em28xx: cx231xx: fix opencoded
 find_and_set_bit()

On 03/12/2023 20:32, Yury Norov wrote:
> Functions in the media/usb drivers opencode find_and_set_bit() by
> polling on a found bit in a while-loop.
> 
> Signed-off-by: Yury Norov <yury.norov@...il.com>

Acked-by: Hans Verkuil <hverkuil-cisco@...all.nl>

Feel free to take this yourself through the bitmap tree.

It's a nice improvement.

Regards,

	Hans

> ---
>  drivers/media/usb/cx231xx/cx231xx-cards.c | 16 ++++------
>  drivers/media/usb/em28xx/em28xx-cards.c   | 37 +++++++++--------------
>  2 files changed, 21 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/media/usb/cx231xx/cx231xx-cards.c b/drivers/media/usb/cx231xx/cx231xx-cards.c
> index 92efe6c1f47b..b314603932d7 100644
> --- a/drivers/media/usb/cx231xx/cx231xx-cards.c
> +++ b/drivers/media/usb/cx231xx/cx231xx-cards.c
> @@ -1708,16 +1708,12 @@ static int cx231xx_usb_probe(struct usb_interface *interface,
>  		return -ENODEV;
>  
>  	/* Check to see next free device and mark as used */
> -	do {
> -		nr = find_first_zero_bit(&cx231xx_devused, CX231XX_MAXBOARDS);
> -		if (nr >= CX231XX_MAXBOARDS) {
> -			/* No free device slots */
> -			dev_err(d,
> -				"Supports only %i devices.\n",
> -				CX231XX_MAXBOARDS);
> -			return -ENOMEM;
> -		}
> -	} while (test_and_set_bit(nr, &cx231xx_devused));
> +	nr = find_and_set_bit(&cx231xx_devused, CX231XX_MAXBOARDS);
> +	if (nr >= CX231XX_MAXBOARDS) {
> +		/* No free device slots */
> +		dev_err(d, "Supports only %i devices.\n", CX231XX_MAXBOARDS);
> +		return -ENOMEM;
> +	}
>  
>  	udev = usb_get_dev(interface_to_usbdev(interface));
>  
> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
> index 4d037c92af7c..af4809fe74a8 100644
> --- a/drivers/media/usb/em28xx/em28xx-cards.c
> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
> @@ -3684,17 +3684,14 @@ static int em28xx_duplicate_dev(struct em28xx *dev)
>  		return -ENOMEM;
>  	}
>  	/* Check to see next free device and mark as used */
> -	do {
> -		nr = find_first_zero_bit(em28xx_devused, EM28XX_MAXBOARDS);
> -		if (nr >= EM28XX_MAXBOARDS) {
> -			/* No free device slots */
> -			dev_warn(&dev->intf->dev, ": Supports only %i em28xx boards.\n",
> -				 EM28XX_MAXBOARDS);
> -			kfree(sec_dev);
> -			dev->dev_next = NULL;
> -			return -ENOMEM;
> -		}
> -	} while (test_and_set_bit(nr, em28xx_devused));
> +	nr = find_and_set_bit(em28xx_devused, EM28XX_MAXBOARDS);
> +	if (nr >= EM28XX_MAXBOARDS) {
> +		/* No free device slots */
> +		dev_warn(&dev->intf->dev, ": Supports only %i em28xx boards.\n", EM28XX_MAXBOARDS);
> +		kfree(sec_dev);
> +		dev->dev_next = NULL;
> +		return -ENOMEM;
> +	}
>  	sec_dev->devno = nr;
>  	snprintf(sec_dev->name, 28, "em28xx #%d", nr);
>  	sec_dev->dev_next = NULL;
> @@ -3827,17 +3824,13 @@ static int em28xx_usb_probe(struct usb_interface *intf,
>  	udev = usb_get_dev(interface_to_usbdev(intf));
>  
>  	/* Check to see next free device and mark as used */
> -	do {
> -		nr = find_first_zero_bit(em28xx_devused, EM28XX_MAXBOARDS);
> -		if (nr >= EM28XX_MAXBOARDS) {
> -			/* No free device slots */
> -			dev_err(&intf->dev,
> -				"Driver supports up to %i em28xx boards.\n",
> -			       EM28XX_MAXBOARDS);
> -			retval = -ENOMEM;
> -			goto err_no_slot;
> -		}
> -	} while (test_and_set_bit(nr, em28xx_devused));
> +	nr = find_and_set_bit(em28xx_devused, EM28XX_MAXBOARDS);
> +	if (nr >= EM28XX_MAXBOARDS) {
> +		/* No free device slots */
> +		dev_err(&intf->dev, "Driver supports up to %i em28xx boards.\n", EM28XX_MAXBOARDS);
> +		retval = -ENOMEM;
> +		goto err_no_slot;
> +	}
>  
>  	/* Don't register audio interfaces */
>  	if (intf->altsetting[0].desc.bInterfaceClass == USB_CLASS_AUDIO) {