Arnold has three global settings for linearizing input data by applying an inverse-gamma correction. By default, texture maps, light colors, and shader colors are assumed to be already linear, but if you need to linearize them, set the gammas to 2.2.

C:\solidangle\Arnold-4.1.3.3\bin>kick -info options | find "gamma"
FLOAT         texture_gamma                     1
FLOAT         light_gamma                       1
FLOAT         shader_gamma                      1

Notes

• The texture_gamma applies only to non-floating point textures. Floating point (Half, Float) textures are assumed linear.
• Texture maps used to control things like normals, displacement, and opacity, will also be linearized if you set texture_gamma to 2.2.
• The light and shader gammas apply to colors picked from color swatches in the application UI (that is, color ports that don’t have a shader tree plugged into them).

In plugins like SItoA and MtoA, you can find these gamma settings in the global render options.

I guess I should mention that in Softimage, you could use the built-in color management and leave these all set to 1.