---------- Forwarded message ---------- From: arun k <arunkarunakaran08@xxxxxxxxx> Date: Wed, Aug 5, 2015 at 12:57 PM Subject: Re: USB - Generic Serial device : Unable to read more than 4095 bytes To: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>, linux-usb@xxxxxxxxxxxxxxx > Ok, but does the sending device know how to process in-band software flow control > and is it set up to respond properly? I am not sure about this. I need to check this. > Also, I doubt software flow control is going to work @ 4Mbaud line rate. > If you're stuck using software flow control, start with a 115kbaud line rate > and see if that fixes your data loss problem I tried B115200 also but issue is still there. I am using a USB device and that sending data at a rate of 409600 bytes/sec. Is this data rate have any relation with issue. Regards, Arun On Wed, Aug 5, 2015 at 11:24 AM, Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> wrote: > > On 08/04/2015 10:00 PM, arun k wrote: > > I enabled software flow control like below > > > > tty.c_iflag |= (IXON | IXOFF | IXANY); > > Ok, but does the sending device know how to process in-band software flow control > and is it set up to respond properly? > > Also, I doubt software flow control is going to work @ 4Mbaud line rate. > If you're stuck using software flow control, start with a 115kbaud line rate > and see if that fixes your data loss problem. > > Regards, > Peter Hurley > > > > On Wed, Aug 5, 2015 at 12:59 AM, Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> wrote: > >> On 08/03/2015 10:47 PM, arun k wrote: > >>> Thank you for the reply > >>> > >>>>> The tty layer is limiting you, just keep reading in a loop until you > >>>>> run out of data, you should not ever expect to read a specific number of > >>>>> bytes from a tty device at a time, the read call will tell you the > >>>>> number that was read properly. > >>> > >>> I tried this method but in my case I found data loss. By changing any buffer size modification in driver side , can we fix this issue ? > >> > >> The data loss is probably occurring because you have all flow control disabled > >> and the line speed is too fast for no flow control. > >> > >> Regards, > >> Peter Hurley > >> > >>>>> Please don't use the "generic" driver, it's slow and not the best to > >>>>> use > >>> > >>> Could you tell me is generic driver is suitable for my application ( My usb device sending data at a rate of 409600 bytes/sec) , ? > >>> or do you have any other suggestion for me ? > >>> > >>> My Linux kernel version is 3.4.35 > >>> > >>> Regards, > >>> Arun > >>> > >>> On Tue, Aug 4, 2015 at 1:13 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx <mailto:gregkh@xxxxxxxxxxxxxxxxxxx>> wrote: > >>> > >>> On Mon, Aug 03, 2015 at 04:44:07PM +0900, arun k wrote: > >>> > Hi , > >>> > > >>> > I have a trouble with using usb serial generic device. > >>> > I am using USB - Generic Serial driver for communicating with my usb > >>> > device and my embedded device. > >>> > >>> Please don't use the "generic" driver, it's slow and not the best to > >>> use. > >>> > >>> > My usb device sending data at a rate of 409600 bytes/sec, and in host > >>> > side application I tried to read 16384 bytes in one read. But the read > >>> > size returning is always 4095 > >>> > >>> The tty layer is limiting you, just keep reading in a loop until you > >>> run out of data, you should not ever expect to read a specific number of > >>> bytes from a tty device at a time, the read call will tell you the > >>> number that was read properly. > >>> > >>> thanks, > >>> > >>> greg k-h > >>> > >>> > >> > -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
