Hi, On Fri, 2009-08-14 at 07:31 -0700, srinivasramana wrote: > 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 > > > > > > > Sorry I didn't get back to your question yet ! I see Greg's helped you in the interim, which is great because I'm a kernel newbie in any case. I've got many years of embedded & mixed signal (RF/HW/SW) behind me, while I mainly specialised in very low power but high performance custom ISM products with my consulting business. So, if it's RF and the likes or OS-less firmware I can help, but Linux I'm still getting my feet wet. Well, that's off my chest in the meantime. Now on with (embedded) Linux studying/playing :-) Good luck. -- 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
