[Linux-parport] Re: [PATCH] register sysfs device for lp devices

[Greg KH]

On Fri, Feb 17, 2006 at 12:38:36PM +0100, Bernhard R. Link wrote:
> Give class_device_create a device pointer parport drivers
> can set via a new parport_set_dev.
> Also patch parport_gsci and parport_pc as example.
> 
> Signed-of-by: Bernhard R Link <brlink at debian.org>
> 
> ---
> 
> Compile and run-tested with linux-2.6.16-rc3-git4.
> 
> Index: mlinux-2.6.15-git12/drivers/char/lp.c
> ===================================================================
> --- mlinux-2.6.15-git12.orig/drivers/char/lp.c	2006-02-10 08:22:48.000000000 +0100
> +++ mlinux-2.6.15-git12/drivers/char/lp.c	2006-02-13 14:46:29.000000000 +0100
> @@ -805,7 +805,7 @@
>  	if (reset)
>  		lp_reset(nr);
>  
> -	class_device_create(lp_class, NULL, MKDEV(LP_MAJOR, nr), NULL,
> +	class_device_create(lp_class, NULL, MKDEV(LP_MAJOR, nr), port->dev,
>  				"lp%d", nr);
>  	devfs_mk_cdev(MKDEV(LP_MAJOR, nr), S_IFCHR | S_IRUGO | S_IWUGO,
>  			"printers/%d", nr);
> Index: mlinux-2.6.15-git12/drivers/parport/parport_gsc.c
> ===================================================================
> --- mlinux-2.6.15-git12.orig/drivers/parport/parport_gsc.c	2006-02-13 14:27:53.000000000 +0100
> +++ mlinux-2.6.15-git12/drivers/parport/parport_gsc.c	2006-02-13 14:46:29.000000000 +0100
> @@ -340,6 +340,9 @@
>  	parport_gsc_write_data(p, 0);
>  	parport_gsc_data_forward (p);
>  
> +	/* Tell sysfs which device is behind this parport */
> +	parport_set_dev (p, &dev->dev);
> +
>  	/* Now that we've told the sharing engine about the port, and
>  	   found out its characteristics, let the high-level drivers
>  	   know about it. */
> Index: mlinux-2.6.15-git12/drivers/parport/parport_pc.c
> ===================================================================
> --- mlinux-2.6.15-git12.orig/drivers/parport/parport_pc.c	2006-02-13 14:30:26.000000000 +0100
> +++ mlinux-2.6.15-git12/drivers/parport/parport_pc.c	2006-02-13 14:46:29.000000000 +0100
> @@ -2340,6 +2340,7 @@
>  	spin_lock(&ports_lock);
>  	list_add(&priv->list, &ports_list);
>  	spin_unlock(&ports_lock);
> +	parport_set_dev (p, &dev->dev);
>  	parport_announce_port (p);
>  
>  	return p;
> Index: mlinux-2.6.15-git12/drivers/parport/share.c
> ===================================================================
> --- mlinux-2.6.15-git12.orig/drivers/parport/share.c	2006-02-13 14:30:26.000000000 +0100
> +++ mlinux-2.6.15-git12/drivers/parport/share.c	2006-02-13 14:46:29.000000000 +0100
> @@ -341,6 +341,11 @@
>  
>  	tmp->waithead = tmp->waittail = NULL;
>  
> +	/*
> +	 * no sysfs device known unless the announcer sets it before
> +	 */
> +	tmp->dev = NULL;
> +

This is not needed, as tmp is zeroed out earlier in the function.


>  	return tmp;
>  }
>  
> Index: mlinux-2.6.15-git12/include/linux/parport.h
> ===================================================================
> --- mlinux-2.6.15-git12.orig/include/linux/parport.h	2006-02-13 14:30:42.000000000 +0100
> +++ mlinux-2.6.15-git12/include/linux/parport.h	2006-02-13 14:46:29.000000000 +0100
> @@ -258,6 +258,7 @@
>  	struct semaphore irq;
>  };
>  
> +struct device;
>  /* A parallel port */
>  struct parport {
>  	unsigned long base;	/* base address */
> @@ -313,6 +314,8 @@
>  
>  	struct list_head full_list;
>  	struct parport *slaves[3];
> +
> +	struct device *dev; /* for the sysfs device symlink */
>  };
>  
>  #define DEFAULT_SPIN_TIME 500 /* us */
> @@ -331,6 +334,10 @@
>  struct parport *parport_register_port(unsigned long base, int irq, int dma,
>  				      struct parport_operations *ops);
>  
> +/* parport_set_dev set the generic device behind this port, so drivers
> + * can display it in their sysfs nodes */
> +#define parport_set_dev(port,devptr) ((port)->dev = (devptr))

If you are going to save off a pointer to a structure, you need to
increment it's reference count.  You aren't doing that here, and bad
things might happen if it gets removed from under you :(

thanks,

greg k-h