Hi Greg, On Thu, 2009-08-13 at 20:41 -0400, Greg Freemyer wrote: > On Thu, Aug 13, 2009 at 3:52 PM, > srinivasramana<srinivas.ramana@xxxxxxxxx> wrote: > > > > Hi All, > > > > I have been working on the feasibility of having multiple device > > nodes(serial type device) for a single device so that applications can treat > > each of these device nodes as separate devices. > > > > 1. Can i write a tty driver which creates multiple nodes(i will set minors > > to the number of nodes i need) > > 2. Now, If I write from user space on any of these nodes i have seen that it > > comes to the tty drivers write call. > > 3. I want to know how do i link my physical driver with this tty driver? > > 4. If mutiple applications are waiting on read on different nodes, how do i > > wake up a particular read based on the incoming data from hardware(on Rx > > interrupt)? > > > > please help. > > > > Thanks & Regards, > > -- Srinivas R > > > > > > > > srinivasramana wrote: > >> > >> Hi, > >> > >> Thanks for the response. I have explored the option of FIFOs, but the > >> issue is I need Full duplex support from the devices. In that case I will > >> have to use two FIFOs for each device. So, it would be good to know if > >> there is any better option. > >> > >> Also, I was thinking of multiple virtual device nodes with single UART. > >> But, I want to know how do I have these layers communicate? multiple > >> virtual ttys with single UART work? > >> Please suggest. > >> > >> Thanks & Regards, > >> -- Srinivas R > >> > >> > >> matthias-44 wrote: > >>> > >>> Hi, > >>> > >>> Why you don't put everything in user space. So you just need the > >>> driver to communicate with your UART port. > >>> Use pipes for communication between your applications and the > >>> UART-controller-application in user space. > >>> > >>> regards, > >>> Matthias > >>> > >>> 2009/7/19 srinivas ramana <srinivas.ramana@xxxxxxxxx>: > >>>> Hi All, > >>>> > >>>> I have a UART port on my device. A micro controller which drives > >>>> multiple > >>>> other devices is connected to this UART port. > >>>> I need all those devices, connected to micro controller, to be visible > >>>> to > >>>> Linux applications as separate UART devices/ports. > >>>> > >>>> What is the best way to do this? What all driver layers i need to > >>>> add/modify. Please help. > >>>> Thanks in advance. > >>>> > >>>> Note: assume there is a protocol between micro controller & Linux to > >>>> understand which device is requesting service. > >>>> > >>>> Thanks & Regards, > >>>> -- Srinivas R > > I'm going to ignore the electrical aspect of multidrop rs-232, but I > really don't think that works at all. > > Assuming you have somehow overcome that major hurdle, I don't > understand your problem. > > You start with a standard multi-port uart serial driver. Then modify > it such that when data comes in your driver decodes the protocol to > get the address/routing info and delivers the data payload to > appropriate device (/dev/ttyx) as if it were a multi-port device. > > On write, your driver gets data from userspace (/dev/ttyx) and wraps > the comm protocol around it and sends it on its way. > > >From a software perspective none of this unusual, strange, or weird in any way. > > If you think about a 8-port serial card, it works exactly as you > describe. A single hardware driver gets the incoming data from the > card, decodes the cards signaling protocol and delivers the data to > the correct device (/dev/ttyx). And on write, it uses the cards > signalling protocol to tell it which port to send the data out. The > only difference is a hardware card uses hardware registers to control > the routing, where as you have it embedded in the data stream. > > Note: TCP/IP also embeds the routing info in the data stream (ie. the > port). It is a totally standard thing to do. > > Greg > -- > Greg Freemyer > Head of EDD Tape Extraction and Processing team > Litigation Triage Solutions Specialist > http://www.linkedin.com/in/gregfreemyer > Preservation and Forensic processing of Exchange Repositories White Paper - > <http://www.norcrossgroup.com/forms/whitepapers/tng_whitepaper_fpe.html> > > The Norcross Group > The Intersection of Evidence & Technology > http://www.norcrossgroup.com > > -- > To unsubscribe from this list: send an email with > "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx > Please read the FAQ at http://kernelnewbies.org/FAQ > > I'm going to ignore the electrical aspect of multidrop rs-232, but I > really don't think that works at all. That's correct, you _can't_ multidrop with RS232 - electrically that is. (So even stuffing of routing/steering or transport data would be totally pointless) You could multiplex perhaps, but that's not multidrop, of course. Even RS422 by standard is 1 transmitter and multiple receivers, so for a network you need to make one big loop node-to-node and return to the Master. You'd need at least RS485. -- Best regards, Kris -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
