On 17.2.2022 17.16, Greg KH wrote: > On Wed, Feb 16, 2022 at 11:51:49AM +0200, Mathias Nyman wrote: >> To support systems with several xhci controllers with active >> dbc on each xhci we need to use IDR to identify and give >> an index to each port. >> >> Avoid using global struct tty_driver.driver_state for storing >> dbc port pointer as it won't work with several dbc ports >> >> Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> >> --- >> drivers/usb/host/xhci-dbgcap.h | 1 + >> drivers/usb/host/xhci-dbgtty.c | 46 ++++++++++++++++++++++++++++------ >> 2 files changed, 40 insertions(+), 7 deletions(-) >> >> diff --git a/drivers/usb/host/xhci-dbgcap.h b/drivers/usb/host/xhci-dbgcap.h >> index 5f3304a06591..ca04192fdab1 100644 >> --- a/drivers/usb/host/xhci-dbgcap.h >> +++ b/drivers/usb/host/xhci-dbgcap.h >> @@ -100,6 +100,7 @@ struct dbc_ep { >> struct dbc_port { >> struct tty_port port; >> spinlock_t port_lock; /* port access */ >> + int minor; >> >> struct list_head read_pool; >> struct list_head read_queue; >> diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c >> index 059b58f48e3a..d3acc0829ee5 100644 >> --- a/drivers/usb/host/xhci-dbgtty.c >> +++ b/drivers/usb/host/xhci-dbgtty.c >> @@ -10,11 +10,14 @@ >> #include <linux/slab.h> >> #include <linux/tty.h> >> #include <linux/tty_flip.h> >> +#include <linux/idr.h> >> >> #include "xhci.h" >> #include "xhci-dbgcap.h" >> >> static struct tty_driver *dbc_tty_driver; >> +static struct idr dbc_tty_minors; >> +static DEFINE_MUTEX(dbc_tty_minors_lock); > > Why not just use an ida instead? That way you do not need another lock > and it becomes a tiny bit simpler overall. idr seemed like a good way to tie together the minor number (in tty_struct index) to the right dbc_port structure, which contains a pointer to that specific xhci device This way I could find the right dbc_port and store it in tty_struct driver_data in the tty_operations install callback, allowing later tty read and and write calls to find the correct xhci controller from tty_struct driver_data. Looking at it now it might be possible to use just ida instead, and set the tty_struct driver_data right after calling tty_port_register_device(). We should know everything we need there, id (minor), dbc_port, and can probably get the tty_struct from the newly created tty port device somehow. Should dig into tty a bit more for this. > > I'll take this now, but in the future it might be worth to change this. Thanks -Mathias