2008-02-04 13:58:39 bfin_spi_adc.c and copy_from_user()

murti iki (GERMANY)

Message: 50644 hello all,

I would like to ask the reason why there is not a copy_from_user() function in the write function of file operations.

The read function has the copy_to_user() but as far as I see the write() function directly dereferences the buffer

from the kernel space.

I would be most happy if somebody can explain me the idea behind this.

thanks alot

tos

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2008-02-04 16:54:41 Re: bfin_spi_adc.c and copy_from_user()

Michael Hennerich (GERMANY)

Message: 50653

I guess this is just bad code, which tends to work on noMMU.

From an efficiency point of view it’s not a bad idea, however it violates various security aspects.

In case you’re a system designer – and know what you are doing…

However we are going to remove this driver soon, please use the spidev interface for user space access.

-Michael

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2008-02-05 05:49:29 Re: bfin_spi_adc.c and copy_from_user()

murti iki (GERMANY)

Message: 50674 Hello Michael,

Thank you for your answer. Actually I am a little bit confused about the spi documentation.

I would appreciate if you can also help me with the below questions of mine.

1) http://docs.blackfin.uclinux.org/doku.php?id=adsp-spiadc_documentation

tells that there are 2 spi drivers namely linux-2.6.x/drivers/char/spi.c (interrupt driven)

and linux-2.6.x/drivers/char/adsp-spiadc.c (dma driven)

however in the linux-2.6.x/drivers/char/ folder there is only bfin_spi_adc.c

I have double checked but couldn't find them, I have found one driver named spi.c but it's

located in linux-2.6.x/drivers/spi/spi.c (also it doesn't have any ioctl commands)

Where can I find these two drivers? ***

I also cannot find the /linux-2.6.x/documentation/spi/spidev file.

2) I have tried to go through the source files to understand the relation between these source codes to little success. Can you please explain me the connection between below files.

linux-2.6.x/drivers/spi/spi_bfin5xx.c

linux-2.6.x/drivers/spi/spi.c

(Probably I am wrong but) To me these files tend to provide kernel functions so that higher layer drivers can utilize them. In my opinion bfin_spi_adc.c is a higher layer driver than these two however it doesn't seem to utilize them. Maybe these two drivers that I couldn't find utilizes them in a way that a linux-uClinux newbie like me can see it easily.

Mit freundlichen Grüssen

tos

*** I have only downloaded the uClinux-dist-2007R1.1-RC3.

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2008-02-05 06:16:16 Re: bfin_spi_adc.c and copy_from_user()

Michael Hennerich (GERMANY)

Message: 50676 Tos,

the ADSP-SPIADC was obsoleted and removed some time ago, while we introduced the generic SPI bus driver.

It does not longer exist - I therefore removed the documentation o the wiki.

The spidev driver will be in our next release coming soon.

You can check out the 2008R1release using svn.

Gruss,