2011/7/26 Per Forlin [off-list ref]:

quoted

quoted

And I know that init_fault_attr_dentries() can only create a
subdirectory in debugfs root directory. ?But I have a patch which
support for creating it in arbitrary directory. ?Could you take a look
at this? (Note that this patch is based on mmotm and not yet tested)

I looked at your patch and it raised two questions.
I can't use FAULT_ATTR_INITIALIZER since mmc_host is allocated on the
heap. It looks like setup_fault_attr(attr, str) will fail if str is
NULL. How can I initialise the fault_attrs if not stack allocated?
About the boot param initialisation of fault attr. There can only be
one fault_mmc_request boot param for the entire kernel but there is
one fault_attr per host, and there may be many hosts. It would be
convenient if setup_fault_attrs would take (attr, boot_param_name),
look up boot_param_name and use that otherwise set default values.

I think you can define one default fail_attr for boot time configuration
and copy it to per-host fail_attr in mmc_add_host_debugfs().

/* pseudo-code */

static DECLARE_FAULT_ATTR(default_mmc_fail_attr);

static int __init setup_fail_mmc_request(char *str)
{
	return setup_fault_attr(&default_mmc_fail_attr, str);
}
__setup("fail_mmc_request=", setup_fail_mmc_request);

...

void mmc_add_host_debugfs(struct mmc_host *host)
{
	...

#ifdef CONFIG_FAIL_MMC_REQUEST
	host->fail_attr = default_mmc_fail_attr;
	if (!debugfs_create_fault_attr("fail_mmc_request",
					root, &host->fail_attr))
		goto err_node;
#endif
	...
}