Re: [PATCH v3] Bluetooth: Keep MSFT ext info throughout ahci_dev's life cycle

Hi Marcel,

On Mon, Jan 25, 2021 at 7:13 AM Marcel Holtmann [off-list ref] wrote:

Hi Miao-chen,

quoted

This moves msft_do_close() from hci_dev_do_close() to
hci_unregister_dev() to avoid clearing MSFT extension info. This also
avoids retrieving MSFT info upon every msft_do_open() if MSFT extension
has been initialized.

The following test steps were performed.
(1) boot the test device and verify the MSFT support debug log in syslog
(2) restart bluetoothd and verify msft_do_close() doesn't get invoked

Signed-off-by: Miao-chen Chou <redacted>
Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Reviewed-by: Archie Pusaka <redacted>
---
Hi Maintainers,

This patch fixes the life cycle of MSFT HCI extension. The current
symmetric calls to msft_do{open,close} in hci_dev_do_{open,close} cause
incorrect MSFT features during bluetoothd start-up. After the kernel
powers on the controller to register the hci_dev, it performs
hci_dev_do_close() which call msft_do_close() and MSFT data gets wiped
out. And then during the startup of bluetoothd, Adv Monitor Manager
relies on reading the MSFT features from the kernel to present the
feature set of the controller to D-Bus clients. However, the power state
of the controller is off during the init of D-Bus interfaces. As a
result, invalid MSFT features are returned by the kernel, since it was
previously wiped out due to hci_dev_do_close().

then just keep the values around and not wipe them. However I prefer still to keep the symmetry and re-read the value every time we init. We can make sure to release the msft_data on unregister.

This patch does exactly what you described - keep the values around
and not wipe them until unregistration of hdev. Since the only thing
that msft_do_close() does is to release msft_data and reset
hdev->msft_data it to NULL, and that's why I move msft_do_close() from
 hci_dev_do_close() to hci_unregister_dev() to release the msft_data.
If this is about naming, I am happy to change msft_do_close() to
perhaps msft_reset() or something similar. As for msft_do_open(), I
will change it to re-read the msft_data instead of skipping.

Regards,
Miao