On 2019-12-18 02:19, Bart Van Assche wrote:
On 12/17/19 12:56 AM, cang@xxxxxxxxxxxxxx wrote:
Even in the current ufs_bsg.c, it creates two devices, one is ufs-bsg,
one is the char dev node under /dev/bsg. Why this becomes a problem
after make it a module?
I took a look into the pci_driver, it is no different than making
ufs-bsg
a plain device. The only special place about pci_driver is that it has
its
own probe() and remove(), and the probe() in its bus_type calls the
probe() in pci_driver. Meaning the bus->probe() is an intermediate
call
used to pass whatever needed by pci_driver->probe().
Of course we can also do this, but isn't it too much for ufs-bsg?
For our case, calling set_dev_drvdata(bsg_dev, hba) to pass hba to
ufs_bsg.c would be enough.
If you take a look at the V3 patch, the change makes the ufs_bsg.c
much conciser. platform_device_register_data() does everything for us,
initialize the device, set device name, provide the match func,
bus type and release func.
Since ufs-bsg is somewhat not a platform device, we can still add it
as a plain device, just need a few more lines to get it initialized.
This allows us leverage kernel's device driver model. Just like Greg
commented, we don't need to re-implement the mechanism again.
Hi Can,
Since ufs-bsg is not a platform device I think it would be wrong to
model ufs-bsg devices as platform devices.
Please have a look at the bus_register() and bus_unregister()
functions as Greg KH asked. Using the bus abstraction is not that
hard. An example is e.g. available in the scsi_debug driver, namely
the pseudo_lld_bus.
Thanks,
Bart.
Hi Bart,
Yes, I am talking the same here. Since platform device is not an option
for ufs-bsg, to make it a plain device we would need to do
bus_register()
and bus_unregister(). And also do device_initialize() and device_add().
Thanks,
Can Guo.
