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SubjectRe: Moving Com1/2 from interrupts 4/3 via the IO-APIC ?
On Wed, 20 May 1998, Steven Ireland wrote:

#Hi All,
#
#Would it be possible on PC's with IO-APIC's to relocate the interrupts used by
#the motherboard COM ports to the 16+ range and free irq 3 & 4 for use on the
#ISA bus ?

Should be. Here's what you'll need to do to linux/drivers/char/serial.c

struct async_struct rs_table[] = {
/* UART CLK PORT IRQ FLAGS */
{ 0, BASE_BAUD, 0x3F8, 4, STD_COM_FLAGS }, /* ttyS0 */
{ 0, BASE_BAUD, 0x2F8, 3, STD_COM_FLAGS }, /* ttyS1 */
{ 0, BASE_BAUD, 0x3E8, 4, STD_COM_FLAGS }, /* ttyS2 */
{ 0, BASE_BAUD, 0x2E8, 3, STD_COM4_FLAGS }, /* ttyS3 */

Would become:

struct async_struct rs_table[] = {
/* UART CLK PORT IRQ FLAGS */
{ 0, BASE_BAUD, 0x3F8, 17, STD_COM_FLAGS }, /* ttyS0 */
{ 0, BASE_BAUD, 0x2F8, 18, STD_COM_FLAGS }, /* ttyS1 */
{ 0, BASE_BAUD, 0x3E8, 4, STD_COM_FLAGS }, /* ttyS2 */
{ 0, BASE_BAUD, 0x2E8, 3, STD_COM4_FLAGS }, /* ttyS3 */

Where 17 and 18 are the IRQs you want to use. :)

Unless something else in the kernel has a problem with the IRQs you want
to use, that shouldn't be a problem. :)

-Phil R. Jaenke (kernel@nls.net / prj@nls.net)
TheGuyInCharge(tm), Ketyra Designs - We get paid to break stuff :)
Linux pkrea.ketyra.INT 2.0.33 #15 Sat Apr 18 00:40:21 EDT 1998 i586
Linux eiterra.nls.net 2.1.98 #15 Fri May 1 18:21:00 EDT 1998 i586
- Linus says for 'brave people only.' I say 'keep a backup.' - :)
! I reserve the right to bill spammers for my time and disk space !


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