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SubjectRe: [PATCH v4] async: Add cmdline option to specify drivers to be async probed
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On 1/30/19 6:43 PM, Feng Tang wrote:
> Asynchronous driver probing can help much on kernel fastboot, and
> this option can provide a flexible way to optimize and quickly verify
> async driver probe.
>
> Also it will help in below cases:
> * Some driver actually covers several families of HWs, some of which
> could use async probing while others don't. So we can't simply
> turn on the PROBE_PREFER_ASYNCHRONOUS flag in driver, but use this
> cmdline option, like igb driver async patch discussed at
> https://www.spinics.net/lists/netdev/msg545986.html
>
> * For SOC (System on Chip) with multiple spi or i2c controllers, most
> of the slave spi/i2c devices will be assigned with fixed controller
> number, while async probing may make those controllers get different
> index for each boot, which prevents those controller drivers to be
> async probed. For platforms not using these spi/i2c slave devices,
> they can use this cmdline option to benefit from the async probing.
>
> Suggested-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> Cc: Randy Dunlap <rdunlap@infradead.org>
> Signed-off-by: Feng Tang <feng.tang@intel.com>
> ---
> Changelog:
> v4:
> Add description to kernel-parameters.txt and refine the

The doc update looks good, but I don't really see the refinement of
the printk message. It still contains the incorrect cmdline option name.


> prink message, as suggested by Randy Dunlap
>
> v3:
> move the cmdline_requested_async_probing() into "default:"
> part to enforce the PROBE_FORCE_SYNCHRONOUS check, as suggested
> by Alexander Duyck
>
> v2:
> * change Alexander Duyck's email to alexander.h.duyck@linux.intel.com
> * fix the parameter for strlcpy()
>
> Documentation/admin-guide/kernel-parameters.txt | 4 ++++
> drivers/base/dd.c | 24 ++++++++++++++++++++++++
> 2 files changed, 28 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index b799bcf..a5b2112 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -910,6 +910,10 @@
> The filter can be disabled or changed to another
> driver later using sysfs.
>
> + driver_async_probe= [KNL]
> + List of driver names to be probed asynchronously.
> + Format: <driver_name1>,<driver_name2>...
> +
> drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
> Broken monitors, graphic adapters, KVMs and EDIDless
> panels may send no or incorrect EDID data sets.
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 8ac10af..279204a 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -57,6 +57,10 @@ static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
> static struct dentry *deferred_devices;
> static bool initcalls_done;
>
> +/* Save the async probe drivers' name from kernel cmdline */
> +#define ASYNC_DRV_NAMES_MAX_LEN 256
> +static char async_probe_drv_names[ASYNC_DRV_NAMES_MAX_LEN];
> +
> /*
> * In some cases, like suspend to RAM or hibernation, It might be reasonable
> * to prohibit probing of devices as it could be unsafe.
> @@ -674,6 +678,23 @@ int driver_probe_device(struct device_driver *drv, struct device *dev)
> return ret;
> }
>
> +static inline bool cmdline_requested_async_probing(const char *drv_name)
> +{
> + return parse_option_str(async_probe_drv_names, drv_name);
> +}
> +
> +/* The option format is "driver_async_probe=drv_name1,drv_name2,..." */
> +static int __init save_async_options(char *buf)
> +{
> + if (strlen(buf) >= ASYNC_DRV_NAMES_MAX_LEN)
> + printk(KERN_WARNING
> + "Too long list of driver names for 'async_probe_drv_names'!\n");

should be 'driver_async_probe'

> +
> + strlcpy(async_probe_drv_names, buf, ASYNC_DRV_NAMES_MAX_LEN);
> + return 0;
> +}
> +__setup("driver_async_probe=", save_async_options);
> +
> bool driver_allows_async_probing(struct device_driver *drv)
> {
> switch (drv->probe_type) {
> @@ -684,6 +705,9 @@ bool driver_allows_async_probing(struct device_driver *drv)
> return false;
>
> default:
> + if (cmdline_requested_async_probing(drv->name))
> + return true;
> +
> if (module_requested_async_probing(drv->owner))
> return true;
>
>

thanks.
--
~Randy

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