Hi Greg/Kris, >> you _can't_ multidrop with RS232 Thats correct. I am not attempting to multidrop RS232. I have a micro controller handling all my devices and that micon connects to the host over UART. Basically, my need is to make each of those devices connected to micon appear in linux as serial devices so that I can make use of my existing applications.(also wide range of applications available for serial devices). So, i have been looking into the multiport serial card drivers. I understood that the tty driver can create the multiple nodes required. I couldn't find yet how to connect my tty driver to the UART driver. As per my UART driver understanding, it happens in uart_add_one_port(). But how do I do that when I am working top to down(tty to uart)? Also, since i have single physical UART port, i believe interrupt handling is just like normal serial driver. please correct me if this is wrong. Suppose I have 4 nodes and applications are waiting on all these 4 nodes for read, when i do tty_flip_buffer_push() in my Rx ISR, which app thread gets unblocked and get the data? Thanks & Regards, -- Srinivas R Microbit_Ubuntu wrote: > > 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 > > > -- View this message in context: http://www.nabble.com/Single-UART-handling-multiple-devices.-tp24554623p24972693.html Sent from the kernelnewbies mailing list archive at Nabble.com. -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
