[PATCH v2 8/8] serial: Add ability to specify MMIO ports via 'serial'

[Benjamin Herrenschmidt]

From: Benjamin Herrenschmidt <benh@amazon.com>

This adds the ability to explicitely add an MMIO based serial port
via the 'serial' command. The syntax is:

serial --port=mmio,<hex_address>{.b,.w,.l,.q}

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
 docs/grub.texi          | 26 ++++++++++++++++++--
 grub-core/term/serial.c | 53 +++++++++++++++++++++++++++++++++++++----
 2 files changed, 72 insertions(+), 7 deletions(-)

diff --git a/docs/grub.texi b/docs/grub.texi
index fd22a69fa..502ca2ef7 100644
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -4168,8 +4168,24 @@ Commands usable anywhere in the menu and in the 
command-line.
 @deffn Command serial [@option{--unit=unit}] [@option{--port=port}] 
[@option{--speed=speed}] [@option{--word=word}] [@option{--parity=parity}] 
[@option{--stop=stop}]
 Initialize a serial device. @var{unit} is a number in the range 0-3
 specifying which serial port to use; default is 0, which corresponds to
-the port often called COM1. @var{port} is the I/O port where the UART
-is to be found; if specified it takes precedence over @var{unit}.
+the port often called COM1.
+
+@var{port} is the I/O port where the UART is to be found or, if prefixed
+with @samp{mmio,}, the MMIO address of the UART. If specified it takes
+precedence over @var{unit}.
+
+Additionally, an MMIO address can be suffixed with:
+@itemize @bullet
+@item
+@samp{.b} for bytes access (default)
+@item
+@samp{.w} for 16-bit word access
+@item
+@samp{.l} for 32-bit long word access or
+@item
+@samp{.q} for 64-bit long long word access
+@end itemize
+
 @var{speed} is the transmission speed; default is 9600. @var{word} and
 @var{stop} are the number of data bits and stop bits. Data bits must
 be in the range 5-8 and stop bits must be 1 or 2. Default is 8 data
@@ -4185,6 +4201,12 @@ The serial port is not used as a communication channel 
unless the
 @command{terminal_input} or @command{terminal_output} command is used
 (@pxref{terminal_input}, @pxref{terminal_output}).
 
+Examples:
+@example
+serial --port=3f8 --speed=9600
+serial --port=mmio,fefb0000.l --speed=115200
+@end example
+
 See also @ref{Serial terminal}.
 @end deffn
 
diff --git a/grub-core/term/serial.c b/grub-core/term/serial.c
index ed7b398b7..d374495cb 100644
--- a/grub-core/term/serial.c
+++ b/grub-core/term/serial.c
@@ -152,8 +152,8 @@ grub_serial_find (const char *name)
       break;
 
 #if (defined(__mips__) || defined (__i386__) || defined (__x86_64__)) && 
!defined(GRUB_MACHINE_EMU) && !defined(GRUB_MACHINE_ARC)
-  if (!port && grub_memcmp (name, "port", sizeof ("port") - 1) == 0
-      && grub_isxdigit (name [sizeof ("port") - 1]))
+  if (!port && grub_strncmp (name, "port", grub_strlen ("port")) == 0
+      && grub_isxdigit (name [grub_strlen ("port")]))
     {
       name = grub_serial_ns8250_add_port (grub_strtoul (&name[sizeof ("port") 
- 1],
                                                        0, 16), NULL);
@@ -164,6 +164,49 @@ grub_serial_find (const char *name)
         if (grub_strcmp (port->name, name) == 0)
            break;
     }
+  if (!port && grub_strncmp (name, "mmio,", grub_strlen ("mmio,")) == 0
+      && grub_isxdigit (name [grub_strlen ("mmio,")]))
+    {
+      const char *p1, *p = &name[grub_strlen ("mmio,")];
+      grub_addr_t addr = grub_strtoul (p, &p1, 16);
+      unsigned int acc_size = 1;
+      unsigned int nlen = p1 - p;
+
+      /* Check address validity and general syntax */
+      if (addr == 0 || (p1[0] != '\0' && p1[0] != '.'))
+        return NULL;
+      if (p1[0] == '.')
+        switch(p1[1])
+          {
+          case 'w':
+            acc_size = 2;
+            break;
+          case 'l':
+            acc_size = 3;
+            break;
+          case 'q':
+            acc_size = 4;
+            break;
+          case 'b':
+            acc_size = 1;
+           /* fallthrough */
+         default:
+           /*
+            * Should we abort for an unknown size ? Let's just default
+            * to 1 byte, it would increase the chance that the user who
+            * did a typo can actually see the console.
+            */
+           acc_size = 1;
+          }
+      name = grub_serial_ns8250_add_mmio (addr, acc_size, NULL);
+      if (!name)
+        return NULL;
+
+      FOR_SERIAL_PORTS (port)
+        if (grub_strncmp (port->name, name, nlen) == 0) {
+          break;
+        }
+    }
   if (!port && grub_strcmp (name, "auto") == 0)
     {
       /* Look for an SPCR if any. If not, default to com0 */
@@ -178,9 +221,9 @@ grub_serial_find (const char *name)
 #endif
 
 #ifdef GRUB_MACHINE_IEEE1275
-  if (!port && grub_memcmp (name, "ieee1275/", sizeof ("ieee1275/") - 1) == 0)
+  if (!port && grub_strncmp (name, "ieee1275/", grub_strlen ("ieee1275/")) == 
0)
     {
-      name = grub_ofserial_add_port (&name[sizeof ("ieee1275/") - 1]);
+      name = grub_ofserial_add_port (&name[grub_strlen ("ieee1275/")]);
       if (!name)
        return NULL;
 
@@ -212,7 +255,7 @@ grub_cmd_serial (grub_extcmd_context_t ctxt, int argc, char 
**args)
 
   if (state[OPTION_PORT].set)
     {
-      if (grub_memcmp (state[OPTION_PORT].arg, "mmio", 4) == 0)
+      if (grub_strncmp (state[OPTION_PORT].arg, "mmio,", grub_strlen 
("mmio,")) == 0)
           grub_snprintf(pname, sizeof (pname), "%s", state[1].arg);
       else
           grub_snprintf (pname, sizeof (pname), "port%lx",
-- 
2.34.1