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Fallback to poll mode in this case. The 0xff handling is x86-specific, the surrounding code is guarded with CONFIG_X86 anyway. Signed-off-by: Marek Marczykowski-Górecki Reviewed-by: Roger Pau Monné Reviewed-by: Jan Beulich --- Changes in v6: - wrap the check in additional CONFIG_X86, with appropriate comment Changes in v5: - drop IRQ 0 from the log message Changes in v4: - adjust log message, change it from WARNING to INFO - re-add x86 reference in the commit message Changes in v3: - change back to checking 0xff explicitly - adjust commit message, include spec reference - change warning to match the above Changes in v2: - add log message - extend commit message - code style fix --- xen/drivers/char/ns16550.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c index fb75cee4a13a..b37f67dc7430 100644 --- a/xen/drivers/char/ns16550.c +++ b/xen/drivers/char/ns16550.c @@ -1238,6 +1238,17 @@ pci_uart_config(struct ns16550 *uart, bool_t skip_amt, unsigned int idx) pci_conf_read8(PCI_SBDF(0, b, d, f), PCI_INTERRUPT_LINE) : 0; +#ifdef CONFIG_X86 + /* PCI Local Bus Specification Revision 3.0 defines 0xff value + * as special only for X86 */ + if ( uart->irq == 0xff ) + uart->irq = 0; +#endif + if ( !uart->irq ) + printk(XENLOG_INFO + "ns16550: %pp no legacy IRQ, using poll mode\n", + &PCI_SBDF(0, b, d, f)); + return 0; } }