nvmem: include bit index in cell sysfs file name

Creating sysfs files for all Cells caused a boot failure for linux-6.8-rc1 on
Apple M1, which (in downstream dts files) has multiple nvmem cells that use the
same byte address. This causes the device probe to fail with

[    0.605336] sysfs: cannot create duplicate filename '/devices/platform/soc@200000000/2922bc000.efuse/apple_efuses_nvmem0/cells/efuse@a10'
[    0.605347] CPU: 7 PID: 1 Comm: swapper/0 Tainted: G S                 6.8.0-rc1-arnd-5+ #133
[    0.605355] Hardware name: Apple Mac Studio (M1 Ultra, 2022) (DT)
[    0.605362] Call trace:
[    0.605365]  show_stack+0x18/0x2c
[    0.605374]  dump_stack_lvl+0x60/0x80
[    0.605383]  dump_stack+0x18/0x24
[    0.605388]  sysfs_warn_dup+0x64/0x80
[    0.605395]  sysfs_add_bin_file_mode_ns+0xb0/0xd4
[    0.605402]  internal_create_group+0x268/0x404
[    0.605409]  sysfs_create_groups+0x38/0x94
[    0.605415]  devm_device_add_groups+0x50/0x94
[    0.605572]  nvmem_populate_sysfs_cells+0x180/0x1b0
[    0.605682]  nvmem_register+0x38c/0x470
[    0.605789]  devm_nvmem_register+0x1c/0x6c
[    0.605895]  apple_efuses_probe+0xe4/0x120
[    0.606000]  platform_probe+0xa8/0xd0

As far as I can tell, this is a problem for any device with multiple cells on
different bits of the same address. Avoid the issue by changing the file name
to include the first bit number.

Fixes: 0331c611949f ("nvmem: core: Expose cells through sysfs")
Link: https://github.com/AsahiLinux/linux/blob/bd0a1a7d4/arch/arm64/boot/dts/apple/t600x-dieX.dtsi#L156
Cc:  <regressions@lists.linux.dev>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Rafał Miłecki <rafal@milecki.pl>
Cc: Chen-Yu Tsai <wenst@chromium.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:  <asahi@lists.linux.dev>
Cc: Sven Peter <sven@svenpeter.dev>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Reviewed-by: Eric Curtin <ecurtin@redhat.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20240209163454.98051-1-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/ABI/testing/sysfs-nvmem-cells b/Documentation/ABI/testing/sysfs-nvmem-cells
index 7af70adf3690e3b0b3a3c148a087ecb3f788d54a..c7c9444f92a880ff3f9971fc52f71a0e2756d5f1 100644 (file)
--- a/Documentation/ABI/testing/sysfs-nvmem-cells
+++ b/Documentation/ABI/testing/sysfs-nvmem-cells
@@ -4,18 +4,18 @@ KernelVersion:        6.5
 Contact:       Miquel Raynal <miquel.raynal@bootlin.com>
 Description:
                The "cells" folder contains one file per cell exposed by the
-               NVMEM device. The name of the file is: <name>@<where>, with
-               <name> being the cell name and <where> its location in the NVMEM
-               device, in hexadecimal (without the '0x' prefix, to mimic device
-               tree node names). The length of the file is the size of the cell
-               (when known). The content of the file is the binary content of
-               the cell (may sometimes be ASCII, likely without trailing
-               character).
+               NVMEM device. The name of the file is: "<name>@<byte>,<bit>",
+               with <name> being the cell name and <where> its location in
+               the NVMEM device, in hexadecimal bytes and bits (without the
+               '0x' prefix, to mimic device tree node names). The length of
+               the file is the size of the cell (when known). The content of
+               the file is the binary content of the cell (may sometimes be
+               ASCII, likely without trailing character).
                Note: This file is only present if CONFIG_NVMEM_SYSFS
                is enabled.
 
                Example::
 
-                 hexdump -C /sys/bus/nvmem/devices/1-00563/cells/product-name@d
+                 hexdump -C /sys/bus/nvmem/devices/1-00563/cells/product-name@d,0
                  00000000  54 4e 34 38 4d 2d 50 2d  44 4e         |TN48M-P-DN|
                  0000000a

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 980123fb4dde05d0e5cd4e0cfe5645b24a8d55dc..eb357ac2e54a2a827ad07b9a073d3e76415a000f 100644 (file)
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -460,8 +460,9 @@ static int nvmem_populate_sysfs_cells(struct nvmem_device *nvmem)
        list_for_each_entry(entry, &nvmem->cells, node) {
                sysfs_bin_attr_init(&attrs[i]);
                attrs[i].attr.name = devm_kasprintf(&nvmem->dev, GFP_KERNEL,
-                                                   "%s@%x", entry->name,
-                                                   entry->offset);
+                                                   "%s@%x,%x", entry->name,
+                                                   entry->offset,
+                                                   entry->bit_offset);
                attrs[i].attr.mode = 0444;
                attrs[i].size = entry->bytes;
                attrs[i].read = &nvmem_cell_attr_read;