Hi Hans,
On 30 June 2015 at 09:54, Hans de Goede hdegoede@redhat.com wrote:
Hi,
On 06/30/2015 04:58 PM, Simon Glass wrote:
Hi Hans,
On 30 June 2015 at 06:54, Hans de Goede hdegoede@redhat.com wrote:
Hi,
On 29-06-15 05:45, Simon Glass wrote:
Hi Hans,
On 17 June 2015 at 13:33, Hans de Goede hdegoede@redhat.com wrote:
On an usb stop instead of leaving orphan usb devices behind simply remove
On a usb_stop()
or
On a 'usb stop' command ?
My intention was for both, since I was under the assumption that "usb stop" on the cmdline, was the only caller of usb_stop(), but a quick grep to the sources show that I'm wrong ...
them. This requires CONFIG_DM_DEVICE_REMOVE to be set, so only build usb_stop() when that is set.
This seems a little unfortunate. I can see the reasoning, but do you think this is necessary? I suspect people chasing code size may remove that option and still want to use USB properly.
This was mostly a result of my thinking that usb_stop() is only used on "usb stop" at the cmdline, which I know realize is wrong.
However my quick grep has learned that we do really need CONFIG_DM_DEVICE_REMOVE to properly implement usb_stop():
From common/bootm.c :
#if defined(CONFIG_CMD_USB) /* * turn off USB to prevent the host controller from writing to the * SDRAM while Linux is booting. This could happen (at least for OHCI * controller), because the HCCA (Host Controller Communication Area) * lies within the SDRAM and the host controller writes continously to * this area (as busmaster!). The HccaFrameNumber is for example * updated every 1 ms within the HCCA structure in SDRAM! For more * details see the OpenHCI specification. */ usb_stop(); #endif
And without CONFIG_DM_DEVICE_REMOVE we end up never calling the hcd's remove callback and thus do not properly stop the usb controller.
So this problem of usb_stop() needing CONFIG_DM_DEVICE_REMOVE already exists before this patch. If you want I can split out the adding of the #ifdef in a separate commit, spelling out why usb_stop() MUST have CONFIG_DM_DEVICE_REMOVE in the commit message. Or maybe just move this all to Kconfig and make DM_USB conflict with CONFIG_DM_DEVICE_REMOVE?
I don't think that is necessary, it feels a bit too inflexible. But perhaps you could add a comment to the Kconfig help for CONFIG_DM_DEVICE_REMOVE?
Ok will do.
It is remove() that is needed, not unbind(). Actually I think it is quite unfortunate to make usb_stop() call unbind. It is a waste of time to do this just before booting the kernel - the current design leaves all devices bound (but I hope we can remove() them at some point).
Instead, I wonder if we can remove the children when we probe the bus?
That should work, but I do not really see any advantage in that, removing the children is not that expensive and it feels like a kludge.
That's how it currently works, from what I can see in the code. But since there is a 'usb_started' boolean this is irrelevant.
Also, what happens to children that are in the device tree - i.e. static USB devices like WiFi? The device tree might have parameters for them. Still, that might not matter as I'm not sure that case is handled correctly today.
AFAIK there is no such thing as usb devices in devicetree, which makes sense as usb is a fully discoverable bus.
Sort-of. But as with PCI it is useful to be able to add settings for the devices in some cases. You can match them using vendor/device or interface IDs. Then the driver can access its settings.
That's why I'm suggesting we unbind the devices that are no-longer present.
The result of this commit is best seen in the output of "dm tree" after plugging out an usb hub with 2 devices plugges in and plugging in a keyb. instead, before this commit the output would be:
usb [ + ] `-- sunxi-musb usb_hub [ ] |-- usb_hub usb_mass_st [ ] | |-- usb_mass_storage usb_dev_gen [ ] | `-- generic_bus_0_dev_3 usb_dev_gen [ + ] `-- generic_bus_0_dev_1
Notice the non active usb_hub child and its 2 non active children. The first child being non-active as in this example also causes usb_get_dev_index to return NULL when probing the first child, which results in the usb kbd code not binding to the keyboard.
Although I suspect that could be fixed.
Right, but just removing the children is a much cleaner solution, and also makes the output of "dm tree" properly reflect reality.
True, although you also have 'usb tree' for that. Another option would be to mark devices that were found and remove the others after the scan.
That seems like needless complexity. I believe that simply removing + unbinding the children on usb_stop is the right thing to do, and it also is the KISS solution.
I'm good with the remove(), but less sure about the unbind(). The state of 'dm tree' does not bother me, and I worry that we then limit our ability to use usb_find_child() to locate a device's parameters (i.e. support for more complex devices which need settings might be harder).
For now, can we just leave this alone? I really don't want to re-visit this later.
Regards, Simon