linux-kernel - Re: [PATCH 2/2] staging: axis-fifo: use unique identifiers in device names

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Message-ID: <2025081035-encourage-lend-0a15@gregkh>
Date: Sun, 10 Aug 2025 16:41:57 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Ovidiu Panait <ovidiu.panait.oss@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-staging@...ts.linux.dev
Subject: Re: [PATCH 2/2] staging: axis-fifo: use unique identifiers in device
 names

On Fri, Aug 08, 2025 at 11:48:31PM +0300, Ovidiu Panait wrote:
> Axis-fifo devices use physical addresses in their name, for example
> 'axis_fifo_0x43c00000'. This is generally frowned upon and it does not
> follow the usual naming scheme that uses unique identifiers.
> 
> Therefore, use ida_alloc()/ida_free() to implement unique identifiers
> for axis-fifo device names (i.e. axis-fifo0, axis-fifo1, etc.).
> 
> Signed-off-by: Ovidiu Panait <ovidiu.panait.oss@...il.com>
> ---
>  drivers/staging/axis-fifo/axis-fifo.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/staging/axis-fifo/axis-fifo.c b/drivers/staging/axis-fifo/axis-fifo.c
> index 06f7cfab4c6a..27e12af25bc7 100644
> --- a/drivers/staging/axis-fifo/axis-fifo.c
> +++ b/drivers/staging/axis-fifo/axis-fifo.c
> @@ -107,6 +107,8 @@
>  static long read_timeout = 1000; /* ms to wait before read() times out */
>  static long write_timeout = 1000; /* ms to wait before write() times out */
>  
> +static DEFINE_IDA(axis_fifo_ida);
> +
>  /* ----------------------------
>   * module command-line arguments
>   * ----------------------------
> @@ -123,6 +125,7 @@ MODULE_PARM_DESC(write_timeout, "ms to wait before blocking write() timing out;
>   */
>  
>  struct axis_fifo {
> +	int id;
>  	int irq; /* interrupt */
>  	void __iomem *base_addr; /* kernel space memory */
>  
> @@ -698,10 +701,6 @@ static int axis_fifo_probe(struct platform_device *pdev)
>  
>  	dev_dbg(fifo->dt_device, "remapped memory to 0x%p\n", fifo->base_addr);
>  
> -	/* create unique device name */
> -	snprintf(device_name, 32, "%s_%pa", DRIVER_NAME, &r_mem->start);
> -	dev_dbg(fifo->dt_device, "device name [%s]\n", device_name);
> -
>  	/* ----------------------------
>  	 *          init IP
>  	 * ----------------------------
> @@ -737,6 +736,11 @@ static int axis_fifo_probe(struct platform_device *pdev)
>  	 *      init char device
>  	 * ----------------------------
>  	 */
> +	fifo->id = ida_alloc(&axis_fifo_ida, GFP_KERNEL);
> +	if (fifo->id < 0)
> +		return fifo->id;
> +
> +	snprintf(device_name, 32, "%s%d", DRIVER_NAME, fifo->id);
>  
>  	/* create character device */
>  	fifo->miscdev.fops = &fops;
> @@ -744,8 +748,10 @@ static int axis_fifo_probe(struct platform_device *pdev)
>  	fifo->miscdev.name = device_name;
>  	fifo->miscdev.parent = dev;
>  	rc = misc_register(&fifo->miscdev);
> -	if (rc < 0)
> +	if (rc < 0) {
> +		ida_free(&axis_fifo_ida, fifo->id);
>  		return rc;
> +	}
>  
>  	axis_fifo_debugfs_init(fifo);
>  
> @@ -759,6 +765,7 @@ static void axis_fifo_remove(struct platform_device *pdev)
>  
>  	debugfs_remove(fifo->debugfs_dir);
>  	misc_deregister(&fifo->miscdev);
> +	ida_free(&axis_fifo_ida, fifo->id);

Did you forget to call ida_destroy() when the module is unloaded?

thanks,

greg k-h