Re: poll

[Ben Greear <greearb@candelatech.com>]

Richard B. Johnson wrote:
> On Thu, 17 Jun 2004, Ben Greear wrote:
> 
> 
>>Richard B. Johnson wrote:
>>
>>>Hello,
>>>Is it okay to use the 'extra' bits in the poll return value for
>>>something? In other words, is the kernel going to allow a user-space
>>>program to define some poll-bits that it waits for, these bits
>>>having been used in the driver?
>>
>>Can't you just do a read and determine from the results of the read
>>what you actually got?  If not, add framing to your message so that
>>you *CAN* determine one message type from another...
>>
>>Ben
>>
> 
> 
> The mailbox read(s) is/are 32-bit int(s). There is no way to identify
> it as being "new" or something that was written two weeks ago.
> That's why we use poll. Poll says 'I got something new for you'.

Then use 3 different file descriptors to poll/read.  That seems more
efficient anyway as it doesn't wake the folks who don't care.

Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com