net: ipa: clean up header memory validation

Do some general cleanup in ipa_cmd_header_valid():
  - Delay assigning the mem variable until just before it's used.
  - Assign the maximum offset and size values together.
  - Improve comments explaining the single range of memory being
    made up of a modem portion and an AP portion.
  - Record the offset of the combined range in a local variable.
  - Do the initial size assignment right after assigning the offset.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ipa/ipa_cmd.c b/drivers/net/ipa/ipa_cmd.c
index 525cdf2..3e5f10d 100644 (file)
--- a/drivers/net/ipa/ipa_cmd.c
+++ b/drivers/net/ipa/ipa_cmd.c
@@ -200,41 +200,53 @@ bool ipa_cmd_table_valid(struct ipa *ipa, const struct ipa_mem *mem,
 /* Validate the memory region that holds headers */
 static bool ipa_cmd_header_valid(struct ipa *ipa)
 {
-       const struct ipa_mem *mem = &ipa->mem[IPA_MEM_MODEM_HEADER];
        struct device *dev = &ipa->pdev->dev;
+       const struct ipa_mem *mem;
        u32 offset_max;
        u32 size_max;
+       u32 offset;
        u32 size;
 
-       /* In ipa_cmd_hdr_init_local_add() we record the offset and size
-        * of the header table memory area.  Make sure the offset and size
-        * fit in the fields that need to hold them, and that the entire
-        * range is within the overall IPA memory range.
+       /* In ipa_cmd_hdr_init_local_add() we record the offset and size of
+        * the header table memory area in an immediate command.  Make sure
+        * the offset and size fit in the fields that need to hold them, and
+        * that the entire range is within the overall IPA memory range.
         */
        offset_max = field_max(HDR_INIT_LOCAL_FLAGS_HDR_ADDR_FMASK);
-       if (mem->offset > offset_max ||
-           ipa->mem_offset > offset_max - mem->offset) {
+       size_max = field_max(HDR_INIT_LOCAL_FLAGS_TABLE_SIZE_FMASK);
+
+       /* The header memory area contains both the modem and AP header
+        * regions.  The modem portion defines the address of the region.
+        */
+       mem = &ipa->mem[IPA_MEM_MODEM_HEADER];
+       offset = mem->offset;
+       size = mem->size;
+
+       /* Make sure the offset fits in the IPA command */
+       if (offset > offset_max || ipa->mem_offset > offset_max - offset) {
                dev_err(dev, "header table region offset too large\n");
                dev_err(dev, "    (0x%04x + 0x%04x > 0x%04x)\n",
-                       ipa->mem_offset, mem->offset, offset_max);
+                       ipa->mem_offset, offset, offset_max);
 
                return false;
        }
 
-       size_max = field_max(HDR_INIT_LOCAL_FLAGS_TABLE_SIZE_FMASK);
-       size = ipa->mem[IPA_MEM_MODEM_HEADER].size;
+       /* Add the size of the AP portion to the combined size */
        size += ipa->mem[IPA_MEM_AP_HEADER].size;
 
+       /* Make sure the combined size fits in the IPA command */
        if (size > size_max) {
                dev_err(dev, "header table region size too large\n");
                dev_err(dev, "    (0x%04x > 0x%08x)\n", size, size_max);
 
                return false;
        }
-       if (size > ipa->mem_size || mem->offset > ipa->mem_size - size) {
+
+       /* Make sure the entire combined area fits in IPA memory */
+       if (size > ipa->mem_size || offset > ipa->mem_size - size) {
                dev_err(dev, "header table region out of range\n");
                dev_err(dev, "    (0x%04x + 0x%04x > 0x%04x)\n",
-                       mem->offset, size, ipa->mem_size);
+                       offset, size, ipa->mem_size);
 
                return false;
        }