> -----Original Message----- > From: Mike Frysinger [mailto:vap...@gentoo.org] > Sent: Thursday, August 27, 2009 2:43 PM > To: Hu Mingkai-B21284 > Cc: u-boot@lists.denx.de; Fleming Andy-AFLEMING > Subject: Re: [U-Boot] [PATCH 3/7] eSPI: add eSPI controller support > > On Thursday 27 August 2009 02:27:30 Hu Mingkai-B21284 wrote: > > > but what if you dont know the length of the transaction ahead of > > > time ? if you look at the spi flash framework, it'll write a few > > > bytes (like the opcode to read the status > > > register) and then it'll just keep reading 1 byte at a > time (polling > > > the status register). there is no way of knowing the > length ahead > > > of time. most of the SPI code in u-boot operates this way. > > > > So the driver use the length passed by SPI flash read function. > > If the length is greater than the max value that is limited by the > > transaction length register's bitfiled, the driver couldn't read > > anything. > > the length used by the first read covers just the length of > the opcode, not any of the data returned by the part > > as long as your driver rejects all of these things, it'll be > detected at runtime and it should be fine to merge -mike >
So the driver combine the opcode length and the data length together, then pass to spi_xfer(for eSPI) . When return the read results, skip the first opcode length bytes. Thanks, Mingkai _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
