Re: [PATCH] HID: Allow drivers without listeners to remain on the bus
From: Henrik Rydberg <hidden>
Date: 2012-07-17 21:49:55
Hi David,
hid-picolcd and hid-wiimote do not allow any of hidinput, hiddev or hidraw to claim the device but still want to remain on the bus. Hence, if a driver uses the raw_event callback but no listener claimed the device, we still leave it on the bus as the driver probably handles everything by itself. Under some circumstances (eg., hidinput_connect() fails and raw_event set) a device may not be left on the bus even though it has no listeners. But then if hidinput_connect() fails there are bigger issues than a device that is left unhandled. So we can safely use this heuristic to avoid adding another flag for special devices like hid-picolcd and hid-wiimote. This also removes the ugly hack from hid-picolcd as this is no longer required. Signed-off-by: David Herrmann <redacted> --- Hi Jiri I posted another patchset that introduced HID_CLAIMED_OTHER to avoid this heuristic but Henrik convinced me that this trivial check is the cleaner and less intrusive implementation. If you're interested, the old patchset was here: http://thread.gmane.org/gmane.linux.kernel.input/25945 Henrik, can you add your signed-off-by as this was your idea?
Gladly, but I would like to change the wording slightly, since a driver with raw_event set is a listener, and we are still bailing out if there are no listeners at all. The title is thus misleading.
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Thanks David drivers/hid/hid-core.c | 8 ++++++-- drivers/hid/hid-picolcd.c | 4 ---- 2 files changed, 6 insertions(+), 6 deletions(-)diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index 9cdc74e..83ca3ba 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c@@ -1373,8 +1373,12 @@ int hid_connect(struct hid_device *hdev, unsigned int connect_mask) if ((connect_mask & HID_CONNECT_HIDRAW) && !hidraw_connect(hdev)) hdev->claimed |= HID_CLAIMED_HIDRAW; - if (!hdev->claimed) { - hid_err(hdev, "claimed by neither input, hiddev nor hidraw\n"); + /* There are device drivers that do not allow hidinput, hiddev or + * hidraw to be connected but still want to remain on the bus. We + * require that these devices use the raw_event callback. Otherwise, we + * simply remove them from the bus if no listener claimed them. */
How about "Drivers using raw_event() are not required to connect to anything else"?
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+ if (!hdev->claimed && !hdev->driver->raw_event) { + hid_err(hdev, "device has no listeners, quitting\n"); return -ENODEV; }diff --git a/drivers/hid/hid-picolcd.c b/drivers/hid/hid-picolcd.c index 45c3433..74c388d 100644 --- a/drivers/hid/hid-picolcd.c +++ b/drivers/hid/hid-picolcd.c@@ -2613,11 +2613,7 @@ static int picolcd_probe(struct hid_device *hdev, goto err_cleanup_data; } - /* We don't use hidinput but hid_hw_start() fails if nothing is - * claimed. So spoof claimed input. */ - hdev->claimed = HID_CLAIMED_INPUT; error = hid_hw_start(hdev, 0); - hdev->claimed = 0; if (error) { hid_err(hdev, "hardware start failed\n"); goto err_cleanup_data;-- 1.7.11.2
Thanks, Henrik