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bin/47977: [PATCH] usr.sbin/i2cscan: support scans using only 1 byte reads
>Synopsis: [PATCH] usr.sbin/i2cscan: support scans using only 1 byte reads
>Arrival-Date: Sun Jun 30 14:55:00 +0000 2013
>Originator: Thomas Cort
With some ARM SoCs, dm37xx (BeagleBoard-xM) for example, 0 byte writes (i.e.
quick writes) on the i2c bus are not supported. With the dm37xx in particular,
it treats an I2C_CNT value of 0 as 65536. The i2cscan program uses 0 byte
writes to probe devices in almost all of the slave address ranges. The driver
for the dm37xx (src/sys/arch/arm/omap/omap3_i2c.c) returns EINVAL when a zero
byte write is attempted. This means that a lot of devices go undetected by
i2cscan on boards that don't support 0 byte writes.
The Linux equivalent of i2cscan (i2cdetect from i2c-tools) provides a '-r'
command line option to scan using 1 byte reads. The patch linked to below
enables similar functionality in i2cscan. The '-r' command line option will
cause all probes to be 1 byte reads. There is a second patch to update the man
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