Re: [PATCH 6/9] dev-serial: add always-plugged property to ensure USB device is always attached

[Samuel Thibault]

Mark Cave-Ayland, le lun. 26 oct. 2020 08:33:58 +0000, a ecrit:
> Some operating systems will generate a new device ID when a USB device is 
> unplugged
> and then replugged into the USB. If this is done whilst switching between 
> multiple
> applications over a virtual serial port, the change of device ID requires 
> going
> back into the OS/application to locate the new device accordingly.
> 
> Add a new always-plugged property that if specified will ensure that the 
> device
> always remains attached to the USB regardless of the state of the backend
> chardev.
> 
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

> ---
>  hw/usb/dev-serial.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c
> index 92c35615eb..919e25e1d9 100644
> --- a/hw/usb/dev-serial.c
> +++ b/hw/usb/dev-serial.c
> @@ -97,6 +97,7 @@ struct USBSerialState {
>      uint8_t event_chr;
>      uint8_t error_chr;
>      uint8_t event_trigger;
> +    bool always_plugged;
>      QEMUSerialSetParams params;
>      int latency;        /* ms */
>      CharBackend cs;
> @@ -516,12 +517,12 @@ static void usb_serial_event(void *opaque, QEMUChrEvent 
> event)
>          s->event_trigger |= FTDI_BI;
>          break;
>      case CHR_EVENT_OPENED:
> -        if (!s->dev.attached) {
> +        if (!s->always_plugged && !s->dev.attached) {
>              usb_device_attach(&s->dev, &error_abort);
>          }
>          break;
>      case CHR_EVENT_CLOSED:
> -        if (s->dev.attached) {
> +        if (!s->always_plugged && s->dev.attached) {
>              usb_device_detach(&s->dev);
>          }
>          break;
> @@ -556,7 +557,8 @@ static void usb_serial_realize(USBDevice *dev, Error 
> **errp)
>                               usb_serial_event, NULL, s, NULL, true);
>      usb_serial_handle_reset(dev);
>  
> -    if (qemu_chr_fe_backend_open(&s->cs) && !dev->attached) {
> +    if (s->always_plugged || (qemu_chr_fe_backend_open(&s->cs) &&
> +                              !dev->attached)) {
>          usb_device_attach(dev, &error_abort);
>      }
>      s->intr = usb_ep_get(dev, USB_TOKEN_IN, 1);
> @@ -584,6 +586,7 @@ static const VMStateDescription vmstate_usb_serial = {
>  
>  static Property serial_properties[] = {
>      DEFINE_PROP_CHR("chardev", USBSerialState, cs),
> +    DEFINE_PROP_BOOL("always-plugged", USBSerialState, always_plugged, 
> false),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> -- 
> 2.20.1
> 

-- 
Samuel
"...[Linux's] capacity to talk via any medium except smoke signals."
(By Dr. Greg Wettstein, Roger Maris Cancer Center)