Re: [virtio-dev] Re: [PATCH v3] Add virtio-input driver.
On Tue, Mar 24, 2015 at 04:25:14PM +0100, Gerd Hoffmann wrote: > On Di, 2015-03-24 at 15:14 +0100, Michael S. Tsirkin wrote: > > On Tue, Mar 24, 2015 at 02:37:24PM +0100, Gerd Hoffmann wrote: > > > Hi, > > > > > > > > input layer checks it and ignores events not supported (according to > > > > > the > > > > > support bitmaps). > > > > > > > > Right but support bitmaps come from host too, no? > > > > > > Yes, but the driver will not set invalid bits (bitcount argument for the > > > virtinput_cfg_bits() function is the number of valid bits of the > > > specific bitmap). > > > > > > cheers, > > > Gerd > > > > > > > > > > > > > Question: does linux ever get such events from userspace > > as opposed to sending them to userspace? > > Yes, it's possible using the userspace input driver > (CONFIG_INPUT_UINPUT) No, not through uinput (as from kernel POV uinput is also a driver), but users can write into evdev. Sending unknown codes is OK: events of unknown type will be dropped by the input core, unknown event codes will be passed on; users not recognizing event code should simply ignore it. Thanks. -- Dmitry ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [virtio-dev] Re: [PATCH v3] Add virtio-input driver.
On Di, 2015-03-24 at 15:14 +0100, Michael S. Tsirkin wrote: > On Tue, Mar 24, 2015 at 02:37:24PM +0100, Gerd Hoffmann wrote: > > Hi, > > > > > > input layer checks it and ignores events not supported (according to the > > > > support bitmaps). > > > > > > Right but support bitmaps come from host too, no? > > > > Yes, but the driver will not set invalid bits (bitcount argument for the > > virtinput_cfg_bits() function is the number of valid bits of the > > specific bitmap). > > > > cheers, > > Gerd > > > > > > > > Question: does linux ever get such events from userspace > as opposed to sending them to userspace? Yes, it's possible using the userspace input driver (CONFIG_INPUT_UINPUT) cheers, Gerd ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [virtio-dev] Re: [PATCH v3] Add virtio-input driver.
On Tue, Mar 24, 2015 at 02:37:24PM +0100, Gerd Hoffmann wrote: > Hi, > > > > input layer checks it and ignores events not supported (according to the > > > support bitmaps). > > > > Right but support bitmaps come from host too, no? > > Yes, but the driver will not set invalid bits (bitcount argument for the > virtinput_cfg_bits() function is the number of valid bits of the > specific bitmap). > > cheers, > Gerd > > > Question: does linux ever get such events from userspace as opposed to sending them to userspace? -- MST ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [virtio-dev] Re: [PATCH v3] Add virtio-input driver.
Hi, > > input layer checks it and ignores events not supported (according to the > > support bitmaps). > > Right but support bitmaps come from host too, no? Yes, but the driver will not set invalid bits (bitcount argument for the virtinput_cfg_bits() function is the number of valid bits of the specific bitmap). cheers, Gerd ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [virtio-dev] Re: [PATCH v3] Add virtio-input driver.
On Tue, Mar 24, 2015 at 12:46:21PM +0100, Gerd Hoffmann wrote:
> Hi,
>
> > > + spin_lock_irqsave(&vi->lock, flags);
> > > + while ((event = virtqueue_get_buf(vi->evt, &len)) != NULL) {
> > > + input_event(vi->idev,
> > > + le16_to_cpu(event->type),
> > > + le16_to_cpu(event->code),
> > > + le32_to_cpu(event->value));
> >
> > What happens if input layer gets an
> > unexpected event code or value?
>
> input layer checks it and ignores events not supported (according to the
> support bitmaps).
Right but support bitmaps come from host too, no?
> > > +static int virtinput_send_status(struct virtio_input *vi,
> > > + u16 type, u16 code, s32 value)
> > > +{
>
> > This means that caller will get errors if it happens to call
> > send_status at a rate that's faster than host's consumption of them.
> > To me this looks wrong.
> > Poking at input layer, it seems to simply discard errors.
> > Is it always safe to discard status updates?
>
> Typical use case is updating the leds of your keyboard. Loosing one
> update isn't the end of the world. Also that are _very_ low rate
> events, and in case that really actually happens you likely have bigger
> problems anyway ;)
Until QE opens a bug report I guess :)
OK but pls add a comment.
> > > +static void virtinput_cfg_bits(struct virtio_input *vi, int select, int
> > > subsel,
> > > +unsigned long *bits, unsigned int bitcount)
> > > +{
> > > + unsigned int bit;
> > > + size_t bytes;
> > > + u8 *virtio_bits;
> > > +
> > > + bytes = virtinput_cfg_select(vi, select, subsel);
> > > + if (!bytes)
> > > + return;
> >
> > How about limiting bytes to sizeof struct virtio_input_config->u?
>
> It's limited to 256 anyway because size is u8 in config space.
That struct is 128 bytes though.
Also, change bytes and virtinput_cfg_select to be u8 to make this
clearer?
> > > + size = virtinput_cfg_select(vi, VIRTIO_INPUT_CFG_ID_DEVIDS, 0);
> > > + if (size >= 8) {
> >
> > What does 8 mean here? Should be sizeof virtio_input_devids?
>
> Yes, fixed.
>
> > > +struct virtio_input_config {
> > > + __u8select;
> > > + __u8subsel;
> > > + __u8size;
> > > + __u8reserved;
> > > + union {
> > > + char string[128];
> > > + __u8 bitmap[128];
> >
> > I note that neither string nor bitmap are used by
> > driver. What are they in aid of?
>
> Fixed. Just sloppy coding, the name should use u.string, the bitmap
> u.bitmap, instead of just "u" (although for offsetof it doesn't make a
> difference).
>
> cheers,
> Gerd
>
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Re: [virtio-dev] Re: [PATCH v3] Add virtio-input driver.
Hi,
> > + spin_lock_irqsave(&vi->lock, flags);
> > + while ((event = virtqueue_get_buf(vi->evt, &len)) != NULL) {
> > + input_event(vi->idev,
> > + le16_to_cpu(event->type),
> > + le16_to_cpu(event->code),
> > + le32_to_cpu(event->value));
>
> What happens if input layer gets an
> unexpected event code or value?
input layer checks it and ignores events not supported (according to the
support bitmaps).
> > +static int virtinput_send_status(struct virtio_input *vi,
> > +u16 type, u16 code, s32 value)
> > +{
> This means that caller will get errors if it happens to call
> send_status at a rate that's faster than host's consumption of them.
> To me this looks wrong.
> Poking at input layer, it seems to simply discard errors.
> Is it always safe to discard status updates?
Typical use case is updating the leds of your keyboard. Loosing one
update isn't the end of the world. Also that are _very_ low rate
events, and in case that really actually happens you likely have bigger
problems anyway ;)
> > +static void virtinput_cfg_bits(struct virtio_input *vi, int select, int
> > subsel,
> > + unsigned long *bits, unsigned int bitcount)
> > +{
> > + unsigned int bit;
> > + size_t bytes;
> > + u8 *virtio_bits;
> > +
> > + bytes = virtinput_cfg_select(vi, select, subsel);
> > + if (!bytes)
> > + return;
>
> How about limiting bytes to sizeof struct virtio_input_config->u?
It's limited to 256 anyway because size is u8 in config space.
> > + size = virtinput_cfg_select(vi, VIRTIO_INPUT_CFG_ID_DEVIDS, 0);
> > + if (size >= 8) {
>
> What does 8 mean here? Should be sizeof virtio_input_devids?
Yes, fixed.
> > +struct virtio_input_config {
> > + __u8select;
> > + __u8subsel;
> > + __u8size;
> > + __u8reserved;
> > + union {
> > + char string[128];
> > + __u8 bitmap[128];
>
> I note that neither string nor bitmap are used by
> driver. What are they in aid of?
Fixed. Just sloppy coding, the name should use u.string, the bitmap
u.bitmap, instead of just "u" (although for offsetof it doesn't make a
difference).
cheers,
Gerd
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