how to align linux address which is created using kmalloc

I was given a task where I need to send the address(ex: 0x2add0010) to the firmware in which the lower 6 bits are reserved I need to send the address accordingly.

Could you please tell how to align this one as I got this address when I requested the memory through kmalloc()

Thank you,

I suppose you could do something like this.

Code:

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struct alignedmem {
    char alignment[64];  // for 6 bits
    char mem[];  // C99 Flexible Array Member
};

// then if size is the amount you want to malloc, then do
struct alignedmem *mem = kmalloc( sizeof(*mem) + size );

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Now one element of alignment will have an address where the bottom 6 bits has the pattern you desire.
All you then do is pass &mem->alignment[x] to your device.

When you're done, you kfree(mem);

Quote:

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Originally Posted by Salem

Code:

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struct alignedmem {
    char alignment[64];  // for 6 bits
    char mem[];  // C99 Flexible Array Member
};

---

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The alignment[] array actually only has to be 63 bytes long. If you need to offset by 64 bytes to align, then you're already aligned...