mfd: Stop setting refcounting pointers in original mfd_cell arrays

Commit 1e29af62f2b285bd18685da93c3ce8c33ca2d1db ("mfd: Add refcounting
support to mfd_cells") had to drop the "const" keyword on the "cell"
parameter of mfd_add_devices(), as it added the refcounting pointers
to the objects of the passed mfd_cell array itself.

However, the mfd core code operates on copies of the mfd_cell objects,
so there's no need to modify the originally passed objects.

Hence, move the setting of the refcounting pointers from mfd_add_devices()
to mfd_platform_add_cell(), where the copy of the mfd_cell objects is made.
mfd_clone_cell() can just pass (a copy of) the original usage_count
pointer.

This allows to make the "cell" parameter of mfd_add_devices() "const"
again, and avoids future race conditions when registering multiple
instances of the same device in parallel.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

2 files changed, 10 insertions, 9 deletions

diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
index f421586f29fb..8736f4539bc0 100644
--- a/drivers/mfd/mfd-core.c
+++ b/drivers/mfd/mfd-core.c
@@ -63,7 +63,8 @@ int mfd_cell_disable(struct platform_device *pdev)
 EXPORT_SYMBOL(mfd_cell_disable);
 
 static int mfd_platform_add_cell(struct platform_device *pdev,
-                                 const struct mfd_cell *cell)
+                                 const struct mfd_cell *cell,
+                                 atomic_t *usage_count)
 {
         if (!cell)
                 return 0;
@@ -72,11 +73,12 @@ static int mfd_platform_add_cell(struct platform_device *pdev,
         if (!pdev->mfd_cell)
                 return -ENOMEM;
 
+        pdev->mfd_cell->usage_count = usage_count;
         return 0;
 }
 
 static int mfd_add_device(struct device *parent, int id,
-                          const struct mfd_cell *cell,
+                          const struct mfd_cell *cell, atomic_t *usage_count,
                           struct resource *mem_base,
                           int irq_base, struct irq_domain *domain)
 {
@@ -115,7 +117,7 @@ static int mfd_add_device(struct device *parent, int id,
                         goto fail_res;
         }
 
-        ret = mfd_platform_add_cell(pdev, cell);
+        ret = mfd_platform_add_cell(pdev, cell, usage_count);
         if (ret)
                 goto fail_res;
 
@@ -180,7 +182,7 @@ fail_alloc:
 }
 
 int mfd_add_devices(struct device *parent, int id,
-                    struct mfd_cell *cells, int n_devs,
+                    const struct mfd_cell *cells, int n_devs,
                     struct resource *mem_base,
                     int irq_base, struct irq_domain *domain)
 {
@@ -195,8 +197,7 @@ int mfd_add_devices(struct device *parent, int id,
 
         for (i = 0; i < n_devs; i++) {
                 atomic_set(&cnts[i], 0);
-                cells[i].usage_count = &cnts[i];
-                ret = mfd_add_device(parent, id, cells + i, mem_base,
+                ret = mfd_add_device(parent, id, cells + i, cnts + i, mem_base,
                                      irq_base, domain);
                 if (ret)
                         break;
@@ -259,8 +260,8 @@ int mfd_clone_cell(const char *cell, const char **clones, size_t n_clones)
         for (i = 0; i < n_clones; i++) {
                 cell_entry.name = clones[i];
                 /* don't give up if a single call fails; just report error */
-                if (mfd_add_device(pdev->dev.parent, -1, &cell_entry, NULL, 0,
-                                   NULL))
+                if (mfd_add_device(pdev->dev.parent, -1, &cell_entry,
+                                   cell_entry.usage_count, NULL, 0, NULL))
                         dev_err(dev, "failed to create platform device '%s'\n",
                                         clones[i]);
         }
diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h
index cebe97ee98b8..60ced604664f 100644
--- a/include/linux/mfd/core.h
+++ b/include/linux/mfd/core.h
@@ -98,7 +98,7 @@ static inline const struct mfd_cell *mfd_get_cell(struct platform_device *pdev)
 }
 
 extern int mfd_add_devices(struct device *parent, int id,
-                           struct mfd_cell *cells, int n_devs,
+                           const struct mfd_cell *cells, int n_devs,
                            struct resource *mem_base,
                            int irq_base, struct irq_domain *irq_domain);