[PATCH 1/2] UBI: block: Remove __initdata from ubiblock_param_ops

[PATCH 1/2] UBI: block: Remove __initdata from ubiblock_param_ops

[Richard Weinberger]

You cannot mark these parameters as __initdata.
Otherwise the data is gone upon module exit.

Fixes:
[  172.045465] BUG: unable to handle kernel paging request at ffffffffa001db38
[  172.046020] IP: [<ffffffff81067aa4>] destroy_params+0x24/0x50

Signed-off-by: Richard Weinberger <richard@nod.at>
---
 drivers/mtd/ubi/block.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
index 69a74fd..7ff473c 100644
--- a/drivers/mtd/ubi/block.c
+++ b/drivers/mtd/ubi/block.c
@@ -156,7 +156,7 @@ static int __init ubiblock_set_param(const char *val,
 	return 0;
 }
 
-static struct kernel_param_ops ubiblock_param_ops __initdata = {
+static struct kernel_param_ops ubiblock_param_ops = {
 	.set    = ubiblock_set_param,
 };
 module_param_cb(block, &ubiblock_param_ops, NULL, 0);
-- 
1.8.1.4

[PATCH 2/2] UBI: block: Implement kernel_param_ops->get()

[Richard Weinberger]

The ->get() function is not optional.

Signed-off-by: Richard Weinberger <richard@nod.at>
---
 drivers/mtd/ubi/block.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
index 7ff473c..9ef7df7 100644
--- a/drivers/mtd/ubi/block.c
+++ b/drivers/mtd/ubi/block.c
@@ -158,6 +158,7 @@ static int __init ubiblock_set_param(const char *val,
 
 static struct kernel_param_ops ubiblock_param_ops = {
 	.set    = ubiblock_set_param,
+	.get	= param_get_charp,
 };
 module_param_cb(block, &ubiblock_param_ops, NULL, 0);
 MODULE_PARM_DESC(block, "Attach block devices to UBI volumes. Parameter format: block=<path|dev,num|dev,name>.\n"
-- 
1.8.1.4

Re: [PATCH 2/2] UBI: block: Implement kernel_param_ops->get()

[Ezequiel Garcia]

Hi Richard,

On Mar 19, Richard Weinberger wrote:
> The ->get() function is not optional.
> 

[..]
>  static struct kernel_param_ops ubiblock_param_ops = {
>  	.set    = ubiblock_set_param,
> +	.get	= param_get_charp,
>  };
>  module_param_cb(block, &ubiblock_param_ops, NULL, 0);

The comment for the function says they are both optional:

/**
 * module_param_cb - general callback for a module/cmdline parameter
 * @name: a valid C identifier which is the parameter name.
 * @ops: the set & get operations for this parameter.
 * @perm: visibility in sysfs.
 *
 * The ops can have NULL set or get functions.
 */

This has no visibility in sysfs, so I can't see how having a NULL
get() is a problem. What's the issue you're trying to fix here?

Maybe I'm missing something?
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com

Re: [PATCH 2/2] UBI: block: Implement kernel_param_ops->get()

[Richard Weinberger]

Am 19.03.2014 14:15, schrieb Ezequiel Garcia:
> Hi Richard,
> 
> On Mar 19, Richard Weinberger wrote:
>> The ->get() function is not optional.
>>
> 
> [..]
>>  static struct kernel_param_ops ubiblock_param_ops = {
>>  	.set    = ubiblock_set_param,
>> +	.get	= param_get_charp,
>>  };
>>  module_param_cb(block, &ubiblock_param_ops, NULL, 0);
> 
> The comment for the function says they are both optional:
> 
> /**
>  * module_param_cb - general callback for a module/cmdline parameter
>  * @name: a valid C identifier which is the parameter name.
>  * @ops: the set & get operations for this parameter.
>  * @perm: visibility in sysfs.
>  *
>  * The ops can have NULL set or get functions.
>  */
> 
> This has no visibility in sysfs, so I can't see how having a NULL
> get() is a problem. What's the issue you're trying to fix here?
> 
> Maybe I'm missing something?
> 

Maybe I've misread the struct.

struct kernel_param_ops {
        /* How the ops should behave */
        unsigned int flags;
        /* Returns 0, or -errno.  arg is in kp->arg. */
        int (*set)(const char *val, const struct kernel_param *kp);
        /* Returns length written or -errno.  Buffer is 4k (ie. be short!) */
        int (*get)(char *buffer, const struct kernel_param *kp);
        /* Optional function to free kp->arg when module unloaded. */
        void (*free)(void *arg);
};

To me it looks like only ->free is optional.

Thanks,
//richard

Re: [PATCH 2/2] UBI: block: Implement kernel_param_ops->get()

[Richard Weinberger]

Am 19.03.2014 14:15, schrieb Ezequiel Garcia:
> Hi Richard,
> 
> On Mar 19, Richard Weinberger wrote:
>> The ->get() function is not optional.
>>
> 
> [..]
>>  static struct kernel_param_ops ubiblock_param_ops = {
>>  	.set    = ubiblock_set_param,
>> +	.get	= param_get_charp,
>>  };
>>  module_param_cb(block, &ubiblock_param_ops, NULL, 0);
> 
> The comment for the function says they are both optional:
> 
> /**
>  * module_param_cb - general callback for a module/cmdline parameter
>  * @name: a valid C identifier which is the parameter name.
>  * @ops: the set & get operations for this parameter.
>  * @perm: visibility in sysfs.
>  *
>  * The ops can have NULL set or get functions.
>  */
> 
> This has no visibility in sysfs, so I can't see how having a NULL
> get() is a problem. What's the issue you're trying to fix here?
> 
> Maybe I'm missing something?
> 

BTW: I think we can omit ->get() as some other drivers also only have ->set().
Who want the credit for a documentation fix? ;)

Thanks,
//richard

Re: [PATCH 1/2] UBI: block: Remove __initdata from ubiblock_param_ops

[Ezequiel Garcia]

On Mar 19, Richard Weinberger wrote:
> You cannot mark these parameters as __initdata.
> Otherwise the data is gone upon module exit.
> 
> Fixes:
> [  172.045465] BUG: unable to handle kernel paging request at ffffffffa001db38
> [  172.046020] IP: [<ffffffff81067aa4>] destroy_params+0x24/0x50
> 
> Signed-off-by: Richard Weinberger <richard@nod.at>

Acked-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>

Thanks for the fix!
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com

Re: [PATCH 1/2] UBI: block: Remove __initdata from ubiblock_param_ops

[Artem Bityutskiy]

On Wed, 2014-03-19 at 11:43 +0100, Richard Weinberger wrote:
> You cannot mark these parameters as __initdata.
> Otherwise the data is gone upon module exit.
> 
> Fixes:
> [  172.045465] BUG: unable to handle kernel paging request at ffffffffa001db38
> [  172.046020] IP: [<ffffffff81067aa4>] destroy_params+0x24/0x50
> 
> Signed-off-by: Richard Weinberger <richard@nod.at>

Pushed to linux-ubifs.git, thanks!

-- 
Best Regards,
Artem Bityutskiy