On 27/09/17 02:42, Linus Walleij wrote:

On Fri, Sep 22, 2017 at 2:36 PM, Adrian Hunter [off-list ref] wrote:

quoted

Until mmc has blk-mq support fully implemented and tested, add a
parameter use_blk_mq, default to false unless config option MMC_MQ_DEFAULT
is selected.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>

quoted

+config MMC_MQ_DEFAULT
+       bool "MMC: use blk-mq I/O path by default"
+       depends on MMC && BLOCK

I would say:
default y

Why not. SCSI is starting to enable this by default so IMO we should

SCSI didn't manage it yet.

not take the
intermediate step of having this as optional. Otherwise it never gets tested.

The argument that we don't have to take any responsibility for getting
things tested is a poor one.

Anyway, you can always send a patch later to change the default, so why the
hurry to do it now?

Set it to default y and after two kernel releases, if nothing happens, we simply
delete the old block layer path.

quoted

+#ifdef CONFIG_MMC_MQ_DEFAULT
+bool mmc_use_blk_mq = true;
+#else
+bool mmc_use_blk_mq = false;
+#endif
+module_param_named(use_blk_mq, mmc_use_blk_mq, bool, S_IWUSR | S_IRUGO);

Are people really modprobing this so it needs to be a module parameter?

Irrespective of modprobe, the parameter can be changed without re-compiling.

Maybe I'm the only developer stupid enough to just recompile and reboot

Just change the parameter and unbind and rebind the host controller.