PNP: add pnp_eisa_id_to_string()

[deliverable/linux.git] / drivers / pnp / support.c

diff --git a/drivers/pnp/support.c b/drivers/pnp/support.c
index 13c608f5fb302864b7bae16defaf2d95365ea815..e848b794e31293c0591c5e728309bc41cf5c2be9 100644 (file)
--- a/drivers/pnp/support.c
+++ b/drivers/pnp/support.c
@@ -25,3 +25,29 @@ int pnp_is_active(struct pnp_dev *dev)
 }
 
 EXPORT_SYMBOL(pnp_is_active);
+
+/*
+ * Functionally similar to acpi_ex_eisa_id_to_string(), but that's
+ * buried in the ACPI CA, and we can't depend on it being present.
+ */
+void pnp_eisa_id_to_string(u32 id, char *str)
+{
+       id = be32_to_cpu(id);
+
+       /*
+        * According to the specs, the first three characters are five-bit
+        * compressed ASCII, and the left-over high order bit should be zero.
+        * However, the Linux ISAPNP code historically used six bits for the
+        * first character, and there seem to be IDs that depend on that,
+        * e.g., "nEC8241" in the Linux 8250_pnp serial driver and the
+        * FreeBSD sys/pc98/cbus/sio_cbus.c driver.
+        */
+       str[0] = 'A' + ((id >> 26) & 0x3f) - 1;
+       str[1] = 'A' + ((id >> 21) & 0x1f) - 1;
+       str[2] = 'A' + ((id >> 16) & 0x1f) - 1;
+       str[3] = hex_asc((id >> 12) & 0xf);
+       str[4] = hex_asc((id >>  8) & 0xf);
+       str[5] = hex_asc((id >>  4) & 0xf);
+       str[6] = hex_asc((id >>  0) & 0xf);
+       str[7] = '\0';
+}