Thread: What is the meaning of line while((dvp->csr & (READY | ERROR)) == 0)

hi friends
reading article on const , volatile type qualifiers page http://publications.gbdirect.co.uk/c..._volatile.html found following code page.

code:

/* standard c example without const or volatile */ /*  * declare device registers  * whether use int or short  * implementation dependent  */  struct devregs{         unsigned short  csr;    /* control & status */         unsigned short  data;   /* data port */ };  /* bit patterns in csr */ #define error   0x1 #define ready   0x2 #define reset   0x4  /* absolute address of device */ #define devaddr ((struct devregs *)0xffff0004)  /* number of such devices in system */ #define ndevs   4  /*  * busy-wait function read byte device n.  * check range of device number.  * wait until ready or error  * if no error, read byte, return  * otherwise reset error, return 0xffff  */ unsigned int read_dev(unsigned devno){          struct devregs *dvp = devaddr + devno;          if(devno >= ndevs)                 return(0xffff);          while((dvp->csr & (ready | error)) == 0)                 ; /* null - wait till done */          if(dvp->csr & error){                 dvp->csr = reset;                 return(0xffff);         }          return((dvp->data) & 0xff); }

i not able understand meaning of line in bold, can please explain me.
thank you.

basically, line loop until csr equal either ready or error. assume there's thread running somewhere update dvp's csr , data fields. loop check whether or not needs done (we're ready use data or there error.)

Forum The Ubuntu Forum Community Ubuntu Specialised Support Development & Programming Programming Talk [SOLVED] What is the meaning of line while((dvp->csr & (READY | ERROR)) == 0)

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