diff options
Diffstat (limited to 'src/kernel/arch/amd64/driver/serial.c')
| -rw-r--r-- | src/kernel/arch/amd64/driver/serial.c | 27 |
1 files changed, 19 insertions, 8 deletions
diff --git a/src/kernel/arch/amd64/driver/serial.c b/src/kernel/arch/amd64/driver/serial.c index 36b7cfa..4ee8639 100644 --- a/src/kernel/arch/amd64/driver/serial.c +++ b/src/kernel/arch/amd64/driver/serial.c @@ -12,17 +12,27 @@ static volatile ring_t backlog = {(void*)backlog_buf, sizeof backlog_buf, 0, 0}; static const int COM1 = 0x3f8; +static bool COM1_exists = false; + static void accept(VfsReq *req); static void serial_irq(void); static VfsReq *hung_reads = NULL; -void serial_init(void) { vfs_root_register("/kdev/com1", accept); } +void serial_init(void) { + if (COM1_exists) { + vfs_root_register("/kdev/com1", accept); + } +} -static void serial_selftest(void) { - char b = 0x69; +static bool serial_selftest(void) { port_out8(COM1 + 4, 0b00011110); // enable loopback mode - port_out8(COM1, b); - assert(port_in8(COM1) == b); + for (int i = 0; i < 16; i++) { + port_out8(COM1, i); + if (port_in8(COM1) != i) { + return false; + } + } + return true; } void serial_preinit(void) { @@ -38,9 +48,10 @@ void serial_preinit(void) { port_out8(COM1 + 1, 0x01); // enable the Data Ready IRQ port_out8(COM1 + 2, 0b11000111); // enable FIFO with 14-bit trigger level (???) - serial_selftest(); - - port_out8(COM1 + 4, 0b00001111); // enable everything in the MCR + if (serial_selftest()) { + COM1_exists = true; + port_out8(COM1 + 4, 0b00001111); // enable everything in the MCR + } } |