[PATCH v2] hw/i2c/pca954x: Add method to get channels

[Peter Delevoryas <peter@pjd.dev>]

I added this helper in the Aspeed machine file a while ago to help
initialize fuji-bmc i2c devices. This moves it to the official pca954x
file so that other files can use it.

This does something very similar to pca954x_i2c_get_bus, but I think
this is useful when you have a very complicated dts with a lot of
switches, like the fuji dts.

This convenience method lets you write code that produces a flat array
of I2C buses that matches the naming in the dts. After that you can just
add individual sensors using the flat array of I2C buses.

See fuji_bmc_i2c_init to understand this point further.

The fuji dts is here for reference:

https://github.com/torvalds/linux/blob/40cb6373b46/arch/arm/boot/dts/aspeed-bmc-facebook-fuji.dts

Signed-off-by: Peter Delevoryas <peter@pjd.dev>
---

Accidentally included fby35.h in v1 while I was working on some other stuff.

Interdiff against v1:
  diff --git a/include/hw/arm/fby35.h b/include/hw/arm/fby35.h
  deleted file mode 100644
  index 1be3ae9a38..0000000000
  --- a/include/hw/arm/fby35.h
  +++ /dev/null
  @@ -1,13 +0,0 @@
  -/*
  - * Copyright (c) Meta Platforms, Inc. and affiliates. (http://www.meta.com)
  - *
  - * This code is licensed under the GPL version 2 or later. See the COPYING
  - * file in the top-level directory.
  - */
  -
  -#ifndef FBY35_H
  -#define FBY35_H
  -
  -void oby35_cl_soc_i2c_init(AspeedSoCState *s);
  -
  -#endif

 hw/arm/aspeed.c                  | 29 +++++++++--------------------
 hw/i2c/i2c_mux_pca954x.c         | 10 ++++++++++
 include/hw/i2c/i2c_mux_pca954x.h | 13 +++++++++++++
 3 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/hw/arm/aspeed.c b/hw/arm/aspeed.c
index 6fe9b13548..bee8a748ec 100644
--- a/hw/arm/aspeed.c
+++ b/hw/arm/aspeed.c
@@ -793,15 +793,6 @@ static void rainier_bmc_i2c_init(AspeedMachineState *bmc)
     create_pca9552(soc, 15, 0x60);
 }
 
-static void get_pca9548_channels(I2CBus *bus, uint8_t mux_addr,
-                                 I2CBus **channels)
-{
-    I2CSlave *mux = i2c_slave_create_simple(bus, "pca9548", mux_addr);
-    for (int i = 0; i < 8; i++) {
-        channels[i] = pca954x_i2c_get_bus(mux, i);
-    }
-}
-
 #define TYPE_LM75 TYPE_TMP105
 #define TYPE_TMP75 TYPE_TMP105
 #define TYPE_TMP422 "tmp422"
@@ -814,20 +805,18 @@ static void fuji_bmc_i2c_init(AspeedMachineState *bmc)
     for (int i = 0; i < 16; i++) {
         i2c[i] = aspeed_i2c_get_bus(&soc->i2c, i);
     }
-    I2CBus *i2c180 = i2c[2];
-    I2CBus *i2c480 = i2c[8];
-    I2CBus *i2c600 = i2c[11];
 
-    get_pca9548_channels(i2c180, 0x70, &i2c[16]);
-    get_pca9548_channels(i2c480, 0x70, &i2c[24]);
+    pca954x_i2c_get_channels(i2c[2], 0x70, "pca9548", &i2c[16]);
+    pca954x_i2c_get_channels(i2c[8], 0x70, "pca9548", &i2c[24]);
     /* NOTE: The device tree skips [32, 40) in the alias numbering */
-    get_pca9548_channels(i2c600, 0x77, &i2c[40]);
-    get_pca9548_channels(i2c[24], 0x71, &i2c[48]);
-    get_pca9548_channels(i2c[25], 0x72, &i2c[56]);
-    get_pca9548_channels(i2c[26], 0x76, &i2c[64]);
-    get_pca9548_channels(i2c[27], 0x76, &i2c[72]);
+    pca954x_i2c_get_channels(i2c[11], 0x77, "pca9548", &i2c[40]);
+    pca954x_i2c_get_channels(i2c[24], 0x71, "pca9548", &i2c[48]);
+    pca954x_i2c_get_channels(i2c[25], 0x72, "pca9548", &i2c[56]);
+    pca954x_i2c_get_channels(i2c[26], 0x76, "pca9548", &i2c[64]);
+    pca954x_i2c_get_channels(i2c[27], 0x76, "pca9548", &i2c[72]);
     for (int i = 0; i < 8; i++) {
-        get_pca9548_channels(i2c[40 + i], 0x76, &i2c[80 + i * 8]);
+        pca954x_i2c_get_channels(i2c[40 + i], 0x76, "pca9548",
+                                 &i2c[80 + i * 8]);
     }
 
     i2c_slave_create_simple(i2c[17], TYPE_LM75, 0x4c);
diff --git a/hw/i2c/i2c_mux_pca954x.c b/hw/i2c/i2c_mux_pca954x.c
index 3945de795c..6b07804546 100644
--- a/hw/i2c/i2c_mux_pca954x.c
+++ b/hw/i2c/i2c_mux_pca954x.c
@@ -169,6 +169,16 @@ I2CBus *pca954x_i2c_get_bus(I2CSlave *mux, uint8_t channel)
     return pca954x->bus[channel];
 }
 
+void pca954x_i2c_get_channels(I2CBus *bus, uint8_t address,
+                              const char *type_name, I2CBus **channels)
+{
+    I2CSlave *mux = i2c_slave_create_simple(bus, type_name, address);
+    Pca954xClass *pc = PCA954X_GET_CLASS(mux);
+    Pca954xState *pca954x = PCA954X(mux);
+
+    memcpy(channels, pca954x->bus, pc->nchans * sizeof(channels[0]));
+}
+
 static void pca9546_class_init(ObjectClass *klass, void *data)
 {
     Pca954xClass *s = PCA954X_CLASS(klass);
diff --git a/include/hw/i2c/i2c_mux_pca954x.h b/include/hw/i2c/i2c_mux_pca954x.h
index 3dd25ec983..3a676a30a9 100644
--- a/include/hw/i2c/i2c_mux_pca954x.h
+++ b/include/hw/i2c/i2c_mux_pca954x.h
@@ -16,4 +16,17 @@
  */
 I2CBus *pca954x_i2c_get_bus(I2CSlave *mux, uint8_t channel);
 
+/**
+ * Creates an i2c mux and retrieves all of the channels associated with it.
+ *
+ * @bus: the i2c bus where the i2c mux resides.
+ * @address: the address of the i2c mux on the aforementioned i2c bus.
+ * @type_name: name of the i2c mux type to create.
+ * @channels: an output parameter specifying where to return the channels.
+ *
+ * Returns: None
+ */
+void pca954x_i2c_get_channels(I2CBus *bus, uint8_t address,
+                              const char *type_name, I2CBus **channels);
+
 #endif
-- 
2.37.0