[PATCH v3 2/3] mmc: core: add random fault injection

[Akinobu Mita]

2011/7/26 Per Forlin <per.forlin at linaro.org>:
>>> 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
	...
}