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Date: Tue, 24 Feb 2015 00:05:12 -0800
From: Brian Norris <computersforpeace@gmail.com>
To: Rodrigo Freire <rfreire@redhat.com>
Cc: linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
        =?iso-8859-1?Q?J=F6rn?= Engel <joern@logfs.org>,
        Felix Fietkau <nbd@openwrt.org>, dwmw2@infradead.org,
        Herton Krzesinski <hkrzesin@redhat.com>
Subject: Re: [PATCH v3 2/3] mtd: block2mtd: Adds a mtd name and a block
 device timeout option
Message-ID: <20150224080512.GE24441@norris-Latitude-E6410>
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On Sun, Nov 09, 2014 at 07:22:27AM -0500, Rodrigo Freire wrote:
> From: Felix Fietkau <nbd@openwrt.org>
> 
> mtd: block2mtd: Adds a mtd name and a block device timeout option
> 
> This patch adds support to a block2mtd MTD name and allows to specify
> a block device timeout when adding a block2mtd MTD drive.
> Usage: block2mtd=<dev>[,<erasesize>[,<name>[,<timeout>]]]

Hmm, are all 4 required in this order? What if I want to set the timeout
without the erasesize or name? I suppose it's not a requirement for this
patch, but it's probably not hard to handle that as a future
enhancement. e.g. block2mtd=<dev[,[<erasesize>][,[<name>][,<timeout>]]]
so I could do

	block2mtd=/dev/mmcblk0p2,,,4

to set the timeout to 4 seconds.

> The devices will be identified the following way:
> [root@server01 ~]# cat /proc/mtd
> dev:    size   erasesize  name
> mtd0: a0000000 00010000 "rootfs"
> mtd1: 265080000 00010000 "anothername"
> mtd2: acd00000 00010000 "/dev/mmcblk0p2"
> Notice that the device mtd2 was added without specifying a name.
> 
> Signed-off-by: Felix Fietkau <nbd@openwrt.org>
> Signed-off-by: Rodrigo Freire <rfreire@redhat.com>
> Signed-off-by: Herton Krzesinski <herton@redhat.com>
> ---
> V3: Separated on a single patch
> --- a/drivers/mtd/devices/block2mtd.c	2014-11-07 17:16:11.711479312 -0200
> +++ b/drivers/mtd/devices/block2mtd.c	2014-11-07 17:15:14.255464054 -0200
> @@ -25,6 +25,7 @@
>  #include <linux/list.h>
>  #include <linux/init.h>
>  #include <linux/mtd/mtd.h>
> +#include <linux/mtd/partitions.h>
>  #include <linux/mutex.h>
>  #include <linux/mount.h>
>  #include <linux/slab.h>
> @@ -218,7 +219,7 @@ static void block2mtd_free_device(struct
>  
>  
>  static struct block2mtd_dev *add_device(char *devname, int erase_size,
> -		int timeout)
> +		const char *mtdname, int timeout)
>  {
>  #ifndef MODULE
>  	int i;
> @@ -226,6 +227,7 @@ static struct block2mtd_dev *add_device(
>  	const fmode_t mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL;
>  	struct block_device *bdev = ERR_PTR(-ENODEV);
>  	struct block2mtd_dev *dev;
> +	struct mtd_partition *part;
>  	char *name;
>  
>  	if (!devname)
> @@ -282,7 +284,9 @@ static struct block2mtd_dev *add_device(
>  
>  	/* Setup the MTD structure */
>  	/* make the name contain the block device in */
> -	name = kasprintf(GFP_KERNEL, "block2mtd: %s", devname);
> +	if (!mtdname)
> +		mtdname = devname;
> +	name = kstrdup(mtdname, GFP_KERNEL);
>  	if (!name)
>  		goto err_destroy_mutex;
>  
> @@ -301,7 +305,11 @@ static struct block2mtd_dev *add_device(
>  	dev->mtd.priv = dev;
>  	dev->mtd.owner = THIS_MODULE;
>  
> -	if (mtd_device_register(&dev->mtd, NULL, 0)) {
> +	part = kzalloc(sizeof(struct mtd_partition), GFP_KERNEL);

                       sizeof(*part)

> +	part->name = name;
> +	part->offset = 0;
> +	part->size = dev->mtd.size;
> +	if (mtd_device_register(&dev->mtd, part, 1)) {
>  		/* Device didn't get added, so free the entry */
>  		goto err_destroy_mutex;
>  	}
> @@ -309,8 +317,7 @@ static struct block2mtd_dev *add_device(
>  	list_add(&dev->list, &blkmtd_device_list);
>  	pr_info("mtd%d: [%s] erase_size = %dKiB [%d]\n",
>  		dev->mtd.index,
> -		dev->mtd.name + strlen("block2mtd: "),
> -		dev->mtd.erasesize >> 10, dev->mtd.erasesize);
> +		mtdname, dev->mtd.erasesize >> 10, dev->mtd.erasesize);
>  	return dev;
>  
>  err_destroy_mutex:
> @@ -383,7 +390,7 @@ static int block2mtd_setup2(const char *
>  	/* 80 for device, 12 for erase size, 80 for name, 8 for timeout */
>  	char buf[80 + 12 + 80 + 8];
>  	char *str = buf;
> -	char *token[2];
> +	char *token[4];
>  	char *name;
>  	size_t erase_size = PAGE_SIZE;
>  	unsigned long timeout = MTD_DEFAULT_TIMEOUT;
> @@ -397,7 +404,7 @@ static int block2mtd_setup2(const char *
>  	strcpy(str, val);
>  	kill_final_newline(str);
>  
> -	for (i = 0; i < 2; i++)
> +	for (i = 0; i < 4; i++)

Maybe use ARRAY_SIZE(token)?

>  		token[i] = strsep(&str, ",");
>  
>  	if (str) {
> @@ -424,7 +431,13 @@ static int block2mtd_setup2(const char *
>  		}
>  	}
>  
> -	add_device(name, erase_size, timeout);
> +	if (token[2] && (strlen(token[2]) + 1 > 80))
> +		pr_err("mtd device name too long");

Hmm, so it's too long, but you continue? Shouldn't we return here?

> +
> +
> +	if (token[3] && kstrtoul(token[3], 0, &timeout))
> +		pr_err("invalid timeout");

Again, shouldn't we return here? It's best not to just ignore invalid
input.

> +	add_device(name, erase_size, token[2], timeout);
>  
>  	return 0;
>  }
> @@ -458,7 +471,7 @@ static int block2mtd_setup(const char *v
>  
>  
>  module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
> -MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\"");
> +MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>[,<name>[,<timeout>]]]\"");
>  
>  static int __init block2mtd_init(void)
>  {

Brian
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