drivers/analog/dac7554: Add NULL checks after kmm_malloc in dac7554_initialize

[Zepp-Hanzj]

Description

Add missing NULL checks after both kmm_malloc calls in dac7554_initialize() to prevent NULL pointer dereference on allocation failure.

Problem

dac7554_initialize() calls kmm_malloc twice — first for priv (a dac7554_dev_s), then for g_dacdev (a dac_dev_s) — without checking either return value. If either allocation fails, the code immediately dereferences the NULL pointer, causing a crash.

The function's doc comment states "a NULL on failure", but the implementation never returns NULL.

Solution

Add NULL checks for both allocations, following the same pattern already established in mcp3008.c, mcp48xx.c, and mcp47x6.c:

1. After the first kmm_malloc for priv: return NULL if it fails.
2. After the second kmm_malloc for g_dacdev: free priv and return NULL if it fails.

Changes

File: drivers/analog/dac7554.c (+13 lines)

Location (~line 250):

  priv = kmm_malloc(sizeof(struct dac7554_dev_s));
+ if (priv == NULL)
+   {
+     aerr("ERROR: Failed to allocate dac7554_dev_s instance\n");
+     return NULL;
+   }
+
  priv->spi = spi;

  g_dacdev = kmm_malloc(sizeof(struct dac_dev_s));
+ if (g_dacdev == NULL)
+   {
+     aerr("ERROR: Failed to allocate dac_dev_s instance\n");
+     kmm_free(priv);
+     return NULL;
+   }
+
  g_dacdev->ad_ops = &g_dacops;

Verification

✅ Checkpatch: ./tools/checkpatch.sh -g HEAD — All checks pass
✅ Code Review: Pattern matches the existing fixes in mcp3008_initialize() (commit dd5670ed), mcp48xx_initialize() and mcp47x6_initialize() (commit fa1589a6).

Scenario	Before	After
priv alloc fails	NULL deref → crash	Returns NULL safely
g_dacdev alloc fails	NULL deref → crash	Frees priv, returns NULL

Signed-off-by

hanzj hanzjian@zepp.com