[PATCH v2 7/8] dev-serial: add support for setting data_bits in QEMUSerialSetParams

[Mark Cave-Ayland]

Also implement the behaviour reported in Linux's ftdi_sio.c whereby if an 
invalid
data_bits value is provided then the hardware defaults to using 8.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 hw/usb/dev-serial.c | 17 +++++++++++++++++
 hw/usb/trace-events |  1 +
 2 files changed, 18 insertions(+)

diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c
index b9e308dca1..e42ce36295 100644
--- a/hw/usb/dev-serial.c
+++ b/hw/usb/dev-serial.c
@@ -308,6 +308,23 @@ static void usb_serial_handle_control(USBDevice *dev, 
USBPacket *p,
         break;
     }
     case VendorDeviceOutRequest | FTDI_SET_DATA:
+        switch (value & 0xff) {
+        case 7:
+            s->params.data_bits = 7;
+            break;
+        case 8:
+            s->params.data_bits = 8;
+            break;
+        default:
+            /*
+             * According to a comment in Linux's ftdi_sio.c original FTDI
+             * chips fall back to 8 data bits for unsupported data_bits
+             */
+            trace_usb_serial_unsupported_data_bits(bus->busnr, dev->addr,
+                                                   value & 0xff);
+            s->params.data_bits = 8;
+        }
+
         switch (value & FTDI_PARITY) {
         case 0:
             s->params.parity = 'N';
diff --git a/hw/usb/trace-events b/hw/usb/trace-events
index 98ee1c5462..109da521cf 100644
--- a/hw/usb/trace-events
+++ b/hw/usb/trace-events
@@ -327,6 +327,7 @@ usb_serial_handle_control(int bus, int addr, int request, 
int value) "dev %d:%u
 usb_serial_unsupported_parity(int bus, int addr, int value) "dev %d:%u 
unsupported parity %d"
 usb_serial_unsupported_stopbits(int bus, int addr, int value) "dev %d:%u 
unsupported stop bits %d"
 usb_serial_unsupported_control(int bus, int addr, int request, int value) "dev 
%d:%u got unsupported/bogus control 0x%x, value 0x%x"
+usb_serial_unsupported_data_bits(int bus, int addr, int value) "dev %d:%u 
unsupported data bits %d, falling back to 8"
 usb_serial_bad_token(int bus, int addr) "dev %d:%u bad token"
 usb_serial_set_baud(int bus, int addr, int baud) "dev %d:%u baud rate %d"
 usb_serial_set_data(int bus, int addr, int parity, int data, int stop) "dev 
%d:%u parity %c, data bits %d, stop bits %d"
-- 
2.20.1