interrupt driven hvc_console as vio device (final)

Andrew,

Here is the revised hvc_console patch which fixes the issues you were concerned with in the previous patch. Your two concerns were:

1. Yielding in hvc_close(). This was replaced with tty_wait_until_sent() which seem to be built for this exact scenario. I also restructured hvc_close() to be more elegant and less confusing than in the previous patch.

2. Spinlocks in hvc_chars_in_buffer() and hvc_write_room() which simply protected values read from hvc_struct instances. I removed the spinlocks and didn't put in memory barriers because they really weren't needed.

Paul MacKerras approved the architecture portions of the previous incarnation of this patch and I have touched the arch code in this revision. Ben Herrenschmidt, who contributed a portion of the orignal code this patch was based on has signed off on this patch.

Changelog:

This is an hvc_console patch which provides driver and ppc64 architecture fixes to enable the hvc_console driver to register itself as a vio device with the vio bus, provide hotplug add/remove for vty adapters, and act as an interrupt driven driver on Power-5 hardware or remain as a polling driver on Power-4 hardware.

arch/ppc64/kernel/hvconsole.c
-----------------------------------------------------------------------
-Changed hvc_get_chars() and hvc_put_chars() api to take vtermno rather than index number.

-Added hvc_find_vtys() function which walks the bus looking for vterm/vty devices to callback to the hvc_console driver. This provides console output functionality prior to early console init (pre mem init and pre device probe).

include/asm-ppc64/hvconsole.h
-----------------------------------------------------------------------

-Changed hvc_get_chars() and hvc_put_chars() api to take vtermno rather than index number.

-Added hvc_find_vtys() function.

-Added hvc_instantiate() function which is implemented by a console driver wanting to receive a callback of and early console init.

drivers/char/hvc_console.c
-----------------------------------------------------------------------

-Switch khvcd from kernel_threads to kthreads which got rid of deprecated daemonize().

-Added module exit clause to be thorough (not terribly necessary with a console driver of course)

-Added early discovery of vterm/vty adapters by doing a bus walk on early console init which results in hvc_instantiate() callback and addition of the vtermno into a static array of vtermnos supported as console adapters (meaning the console api's work against these vtermnos prior to full console initialization).

-This driver is now registered as a vio driver which means that vty adapters are now managed via probe/remove. This means hvc_console supports hotplug vty adapters.

-Driver now requests more device nodes than what was found on the initial bus walk when registered as a tty driver to make room for hotplug vty adapters. These secondary vty adapters provide a tty tunnel between partitions.

-Removed static hvc_struct array and replaced with a linux list that has elements (hvc_struct instances) added/removed on probe/remove AFTER early console init. This is important because kmalloc can't be done at early console init.

-Driver now either runs in interrupt driven mode or in polling mode on older hardware. The khvcd is smart enough to not 'schedule()' when there are no interrupts.

-kobjects are now used for ref counting on the hvc_struct instances.

-This driver puts the tty layer to sleep on hvc_close() if there are pending data writes being blocked by firmware.

-Removed useless spinlocks in hvc_chars_in_buffer() and hvc_write_room.

Thanks,

Ryan S. Arnold
IBM Linux Technology Center

Whoops, forgot the patch! OK lets try this again, here is the patch!

Changelog:

This is an hvc_console patch which provides driver and ppc64 architecture fixes to enable the hvc_console driver to register itself as a vio device with the vio bus, provide hotplug add/remove for vty adapters, and act as an interrupt driven driver on Power-5 hardware or remain as a polling driver on Power-4 hardware.

arch/ppc64/kernel/hvconsole.c
-----------------------------------------------------------------------
-Changed hvc_get_chars() and hvc_put_chars() api to take vtermno rather than index number.

-Added hvc_find_vtys() function which walks the bus looking for vterm/vty devices to callback to the hvc_console driver. This provides console output functionality prior to early console init (pre mem init and pre device probe).

include/asm-ppc64/hvconsole.h
-----------------------------------------------------------------------

-Changed hvc_get_chars() and hvc_put_chars() api to take vtermno rather than index number.

-Added hvc_find_vtys() function.

-Added hvc_instantiate() function which is implemented by a console driver wanting to receive a callback of and early console init.

drivers/char/hvc_console.c
-----------------------------------------------------------------------

-Switch khvcd from kernel_threads to kthreads which got rid of deprecated daemonize().

-Added module exit clause to be thorough (not terribly necessary with a console driver of course)

-Added early discovery of vterm/vty adapters by doing a bus walk on early console init which results in hvc_instantiate() callback and addition of the vtermno into a static array of vtermnos supported as console adapters (meaning the console api's work against these vtermnos prior to full console initialization).

-This driver is now registered as a vio driver which means that vty adapters are now managed via probe/remove. This means hvc_console supports hotplug vty adapters.

-Driver now requests more device nodes than what was found on the initial bus walk when registered as a tty driver to make room for hotplug vty adapters. These secondary vty adapters provide a tty tunnel between partitions.

-Removed static hvc_struct array and replaced with a linux list that has elements (hvc_struct instances) added/removed on probe/remove AFTER early console init. This is important because kmalloc can't be done at early console init.

-Driver now either runs in interrupt driven mode or in polling mode on older hardware. The khvcd is smart enough to not 'schedule()' when there are no interrupts.

-kobjects are now used for ref counting on the hvc_struct instances.

-This driver puts the tty layer to sleep on hvc_close() if there are pending data writes being blocked by firmware.

-Removed useless spinlocks in hvc_chars_in_buffer() and hvc_write_room.

Ryan S. Arnold
IBM Linux Technology Center

@@ -22,9 +22,19 @@
 #ifndef _PPC64_HVCONSOLE_H
 #define _PPC64_HVCONSOLE_H
 
-extern int hvc_get_chars(int index, char *buf, int count);
-extern int hvc_put_chars(int index, const char *buf, int count);
-extern int hvc_count(int *start_termno);
+/*
+ * This is the max number of console adapters that can/will be found as
+ * console devices on first stage console init.  Any number beyond this range
+ * can't be used as a console device but is still a valid tty device.
+ */
+#define MAX_NR_HVC_CONSOLES	16
 
-#endif /* _PPC64_HVCONSOLE_H */
+extern int hvc_get_chars(uint32_t vtermno, char *buf, int count);
+extern int hvc_put_chars(uint32_t vtermno, const char *buf, int count);
+
+/* Early discovery of console adapters. */
+extern int hvc_find_vtys(void);
 
+/* Implemented by a console driver */
+extern int hvc_instantiate(uint32_t vtermno, int index);
+#endif /* _PPC64_HVCONSOLE_H */