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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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