Re: usb transfer length

[Oliver Neukum]

Am Montag, den 26.02.2018, 16:41 +0200 schrieb Ran Shalit:
> Hello,
> 
> When performing usb transfer we request for maximum size of transfer,
> yet another size of message (shorter or longer) might be sent from
> device to host.
> 
> Are both cases (shorter/longer) legal in usb standard  ?

No. Shorter is OK, longer is not. Remember that USB transfers
are packaged. A transfer is divided into packages. A transfer is
terminated prematurely if a package is not filled to capacity.
I would suggest you get an introductory book and read the kernel's
documentation on the API. Short transfers are described.

HTH
Oliver

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usb transfer length

[Ran Shalit]

Hello,

When performing usb transfer we request for maximum size of transfer,
yet another size of message (shorter or longer) might be sent from
device to host.

Are both cases (shorter/longer) legal in usb standard  ?

In case both are legal:
If it is shorter, I guess there is no issue at all.
If it is longer - the host must perform transfer for the remaining of
the message. Is that correct ?

Thank you,
ranran
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