C - use of a volatile pointer

Question

Why would one create a volatile pointer? And suppose I want a volatile pointer which points to a volatile variable, which of the following declarations would accomplish this:

volatile int *pData;

or

volatile int * volatile pData;

Answer 1

Why would one create a volatile pointer?

Example: To access data whose pointer is updated by a background process.

Stuff * volatile VideoFrame;
for (;;) {
  Block_Changes();
  Stuff MyCopy = *VideoFrame;
  Allow_Changes();
  Use(&MyCopy);
}

I want a volatile pointer which points to a volatile variable, which of the following declarations would accomplish this:

The 2^nd meets the goal. volatile int * volatile pData; is a:
pData as volatile pointer to volatile int

---

The 1^st volatile int *pData; is a non-volatile pointer to volatile data:
pData as pointer to volatile int

The volitle keyword is most often used in this context. @ Eugene Sh.