On Thu, Feb 13, 2025 at 10:56:46AM -0500, Luiz Augusto von Dentz wrote: > Hi Greg, > > On Thu, Feb 13, 2025 at 10:39 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > On Thu, Feb 13, 2025 at 09:22:28AM -0500, Luiz Augusto von Dentz wrote: > > > Hi Greg, > > > > > > On Thu, Feb 13, 2025 at 8:45 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > On Thu, Feb 13, 2025 at 09:33:34PM +0800, Hsin-chen Chuang wrote: > > > > > On Thu, Feb 13, 2025 at 8:10 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > > > > > A: http://en.wikipedia.org/wiki/Top_post > > > > > > Q: Were do I find info about this thing called top-posting? > > > > > > A: Because it messes up the order in which people normally read text. > > > > > > Q: Why is top-posting such a bad thing? > > > > > > A: Top-posting. > > > > > > Q: What is the most annoying thing in e-mail? > > > > > > > > > > > > A: No. > > > > > > Q: Should I include quotations after my reply? > > > > > > > > > > > > http://daringfireball.net/2007/07/on_top > > > > > > > > > > > > On Thu, Feb 13, 2025 at 07:57:15PM +0800, Hsin-chen Chuang wrote: > > > > > > > The btusb driver data is allocated by devm_kzalloc and is > > > > > > > automatically freed on driver detach, so I guess we don't have > > > > > > > anything to do here. > > > > > > > > > > > > What? A struct device should NEVER be allocated with devm_kzalloc. > > > > > > That's just not going to work at all. > > > > > > > > > > Noted. Perhaps that needs to be refactored together. > > > > > > > > > > > > > > > > > > Or perhaps we should move btusb_disconnect's content here? Luiz, what > > > > > > > do you think? > > > > > > > > > > > > I think something is really wrong here. Why are you adding a new struct > > > > > > device to the system? What requires that? What is this new device > > > > > > going to be used for? > > > > > > > > > > The new device is only for exposing a new sysfs attribute. > > > > > > > > That feels crazy. > > > > > > > > > So originally we had a device called hci_dev, indicating the > > > > > implementation of the Bluetooth HCI layer. hci_dev is directly the > > > > > child of the usb_interface (the Bluetooth chip connected through USB). > > > > > Now I would like to add an attribute for something that's not defined > > > > > in the HCI layer, but lower layer only in Bluetooth USB. > > > > > Thus we want to rephrase the structure: usb_interface -> btusb (new > > > > > device) -> hci_dev, and then we could place the new attribute in the > > > > > new device. > > > > > > > > > > Basically I kept the memory management in btusb unchanged in this > > > > > patch, as the new device is only used for a new attribute. > > > > > Would you suggest we revise the memory management since we added a > > > > > device in this module? > > > > > > > > If you add a new device in the tree, it HAS to work properly with the > > > > driver core (i.e. life cycles are unique, you can't have empty release > > > > functions, etc.) Put it on the proper bus it belongs to, bind the > > > > needed drivers to it, and have it work that way, don't make a "fake" > > > > device for no good reason. > > > > > > Well we could just introduce it to USB device, since alternate setting > > > is a concept that is coming from there, but apparently the likes of > > > /sys/bus/usb/devices/usbX/bAlternateSetting is read-only, some > > > Bluetooth profiles (HFP) requires switching the alternate setting and > > > because Google is switching to handle this via userspace thus why > > > there was this request to add a new sysfs to control it. > > > > That's fine, just don't add devices where there shouldn't be devices, or > > if you do, make them actually work properly (i.e. do NOT have empty > > release callbacks...) > > > > If you want to switch alternate settings in a USB device, do it the > > normal way from userspace that has been there for decades! Don't make > > up some other random sysfs file for this please, that would be crazy, > > and wrong. > > > > So what's wrong with the current api we have today that doesn't work for > > bluetooth devices? > > Perhaps it is just lack of knowledge then, how userspace can request > to switch alternate settings? If I recall correctly Hsin-chen tried > with libusb, or something like that, but it didn't work for some > reason. The USBDEVFS_SETINTERFACE usbfs ioctl should do this. If not, pleaase let us know. libusb supports this through the libusb_set_interface_alt_setting() function. Here's an 11 year old stackoverflow question about this: https://stackoverflow.com/questions/17546709/what-does-libusb-set-interface-alt-setting-do thanks, greg k-h
